A/B Testing
A/B testing is an experimental design that randomly assigns participants or users to one of two variants, labeled A and B, to compare their effects on a predefined outcome.
Paperguide Research Reference
Research Glossary
Every term defined with cited sources, real world examples, interactive learning, and the methodological depth that serious research demands. Built for researchers who need precision, not guesswork.
A
Abstract
An abstract is a brief summary of a research article, thesis, or conference paper that describes the study's purpose, methods, results, and conclusions.
Acceptance Rate
The acceptance rate is the proportion of submitted manuscripts that a journal accepts for publication, typically expressed as a percentage.
Action Research
Action research is a participatory research approach that combines systematic investigation with practical action to solve real world problems while simultaneously generating new knowledge.
Active Surveillance
Active surveillance is a public health monitoring method in which health authorities regularly and proactively solicit reports from healthcare providers, laboratories, and other data sources rather than waiting for notifications to arrive passively.
Adaptive Design
An adaptive design is a clinical trial design that allows for prospectively planned modifications to one or more aspects of the trial based on accumulating data from participants, without undermining the study's integrity or validity.
Adverse Drug Reaction
An adverse drug reaction (ADR) is an unintended and harmful response to a medication that occurs at doses normally used for prophylaxis, diagnosis, or treatment.
Adverse Event (AE)
An adverse event is any untoward medical occurrence in a patient or clinical investigation participant administered an intervention, whether or not the event has a causal relationship with the treatment under study.
Allocation Concealment
Allocation concealment is a procedural safeguard used in clinical trials to prevent the person enrolling participants from knowing or predicting the upcoming treatment assignment until the moment of allocation.
Alpha Level
The alpha level, also called the significance level, is the predetermined probability threshold below which the null hypothesis is rejected in a statistical test.
Alternative Hypothesis
The alternative hypothesis, denoted H1 or Ha, is the statement that an effect, difference, or relationship between variables exists in the population being studied.
Altmetrics
Altmetrics, short for alternative metrics, are indicators that measure the attention and impact of research outputs beyond traditional citation counts.
AMSTAR (A MeaSurement Tool to Assess systematic Reviews)
AMSTAR is a validated instrument designed to appraise the methodological quality of systematic reviews.
Ancestry Approach
The ancestry approach is a supplementary search strategy used in systematic reviews to identify additional relevant studies by examining the reference lists of included articles and key review papers.
ANCOVA (Analysis of Covariance)
Analysis of covariance, or ANCOVA, is a statistical method that combines elements of analysis of variance (ANOVA) and linear regression to compare group means on an outcome variable while controlling for one or more continuous covariates.
ANOVA (Analysis of Variance)
Analysis of variance, or ANOVA, is a statistical method that tests whether the means of three or more groups differ significantly from one another.
Applied Research
Applied research is investigation conducted to solve a specific, practical problem or to develop actionable knowledge for a defined context, rather than to advance understanding of abstract phenomena.
Archival Research
Archival research is a method of inquiry that involves analyzing existing records, documents, or datasets that were originally created for purposes other than the current study.
Attack Rate
The attack rate is the proportion of persons exposed to a specific pathogen, toxin, or hazard who develop the disease or condition of interest within a specified time period.
Attrition
Attrition refers to the loss of participants from a study over time due to withdrawal, dropout, loss to follow up, death, or other reasons.
Attrition Bias
Attrition bias is a systematic error that arises when participants who drop out of a study before completion differ in meaningful ways from those who remain, creating differences between groups that are not attributable to the intervention.
Authorship
Authorship is the formal designation of individuals who have made substantial intellectual contributions to a research work.
Automated Screening
Automated screening refers to the use of machine learning, natural language processing, or other computational algorithms to assist in the screening of titles, abstracts, or full texts during systematic reviews.
Automation Bias
Automation bias is the tendency of human decision makers to over rely on the output of automated systems, including artificial intelligence tools, even when contradictory information is available from other sources or from the decision maker's own judgment.
B
Base Case Analysis
The base case analysis is the primary analysis in a health economic evaluation that uses the most plausible, best supported set of assumptions and parameter values.
Basic Research
Basic research, also called pure or fundamental research, is investigation aimed at increasing understanding of underlying principles and phenomena without immediate practical application in mind.
Bayesian Statistics
Bayesian statistics is a branch of statistical inference based on Bayes' theorem that treats probability as a measure of belief or uncertainty rather than as a long run frequency.
Before and After Study
A before and after study, also known as a pre post study, is a research design that measures outcomes in the same group of participants or settings before and after an intervention is implemented, without a separate contemporaneous control group.
Begg Test
The Begg test, also known as the Begg and Mazumdar rank correlation test, is a statistical method used to detect publication bias in meta analysis.
Benefit Risk Analysis
A benefit risk analysis is a systematic evaluation that compares the clinical benefits of a medical intervention (such as a drug, medical device, or procedure) with its associated risks and potential harms.
Bias
Bias is a systematic error in the design, conduct, analysis, or reporting of a study that produces results that consistently deviate from the truth in a particular direction.
Bibliometric Analysis
Bibliometric analysis is the quantitative examination of bibliographic data from published literature to identify patterns, trends, and relationships in scientific production, citation behavior, collaboration networks, and knowledge diffusion.
Bibliometrics
Bibliometrics is the application of quantitative methods to the analysis of scholarly publications, using mathematical and statistical techniques to measure patterns in authorship, citation behavior, publication output, and research collaboration.
Big Data
Big data refers to extremely large and complex datasets that exceed the processing capabilities of conventional data management tools and require advanced computational methods for storage, processing, and analysis.
Biomarker
A biomarker, short for biological marker, is a measurable biological indicator used to assess a normal physiological process, a pathological process, or a pharmacological response to a therapeutic intervention.
Bivariate Analysis
Bivariate analysis is a statistical approach that examines the relationship between exactly two variables simultaneously.
Blinding
Blinding, also called masking, is a procedural safeguard in which study participants, investigators, outcome assessors, data analysts, or other parties are kept unaware of treatment assignments to prevent knowledge of the assigned intervention from…
Budget Impact Analysis
A budget impact analysis (BIA) is a type of health economic evaluation that estimates the financial consequences of adopting a new health intervention within a specific healthcare setting over a defined time horizon, typically three to five years.
C
Case Control Study
A case control study is an observational research design that compares individuals who have a specific disease or outcome (cases) with individuals who do not (controls) to identify factors associated with the occurrence of the outcome.
Case Fatality Rate
The case fatality rate (CFR) is the proportion of persons diagnosed with a particular disease or condition who die from that disease within a specified time period.
Case Study
A case study is a detailed, in depth investigation of a single participant, small group, organization, event, or phenomenon, using multiple sources of evidence to build a comprehensive understanding.
Categorical Data
Categorical data are observations that represent distinct categories or groups rather than measured quantities, with no meaningful quantitative distance between them, even when ordered.
Causal Inference
Causal inference is the process of drawing conclusions about cause and effect relationships from data, using study design features, statistical methods, and theoretical reasoning to distinguish genuine causation from mere correlation or confounded…
Censored Data
Censored data are observations in survival analysis for which the exact time to the event of interest is not known because the event has not yet occurred by the end of the study period, the participant was lost to follow up before the event, or the…
Central Limit Theorem
The central limit theorem (CLT) is a foundational principle in statistics stating that the sampling distribution of the sample mean approaches a normal (Gaussian) distribution as the sample size increases, regardless of the shape of the underlying population…
Chi Square Test
The chi square test is a statistical test that evaluates whether the distribution of observed frequencies across categories differs significantly from the frequencies that would be expected under a specified hypothesis, most commonly the hypothesis of…
Citation
A citation is a reference to a published or unpublished source that identifies the author, title, publication date, and other bibliographic details needed to locate the original work.
Citation Index
A citation index is a database that records the citations each published work receives from subsequent publications, enabling researchers to trace how ideas, methods, and findings propagate through the scholarly literature.
CiteScore
CiteScore is a journal level metric calculated by Scopus that measures the average number of citations received per document published in a journal over a four year citation window.
Clinical Data
Clinical data are information generated from the clinical use of a medical intervention, including data from formal clinical investigations, post market surveillance, published scientific literature, adverse event reports, and routine clinical practice.
Clinical Equipoise
Clinical equipoise is a state of genuine uncertainty within the expert medical community about the comparative therapeutic merits of each treatment arm in a clinical trial.
Clinical Significance
Clinical significance refers to the practical importance of a treatment effect, indicating whether the observed change is large enough to be meaningful in real world patient care.
Clinical Trial
A clinical trial is a prospective research study that assigns human participants to one or more health related interventions to evaluate their effects on clinical outcomes.
Cluster Randomized Trial
A cluster randomized trial is a type of randomized experiment in which randomization occurs at the group level rather than at the individual level.
Cochrane Library
The Cochrane Library is a collection of databases containing high quality, independent evidence to inform healthcare decision making.
Cochrane Review
A Cochrane Review is a systematic review of primary research in healthcare and health policy produced by the Cochrane Collaboration, following a structured, transparent, and pre specified methodology set out in Cochrane's guidance, such as the Cochrane…
Coding
In qualitative research, coding is the analytical process of assigning labels, tags, or categories to segments of data (such as interview transcripts, field notes, or documents) to organize, classify, and interpret them.
Coefficient of Variation
The coefficient of variation (CV) is a standardized measure of dispersion calculated as the ratio of the standard deviation to the mean, typically expressed as a percentage.
Cohort Study
A cohort study is an observational research design that follows a group of individuals who share a common characteristic or exposure over time to determine how certain factors affect the incidence of outcomes.
Common Data Model
A common data model (CDM) is a comprehensive framework that includes standardized definitions, data structures, specifications, and operational rules that allow data from different sources to be organized, presented, and analyzed in a uniform manner.
Community Based Participatory Research
Community based participatory research (CBPR) is a collaborative research approach in which community members, organizational representatives, and academic researchers jointly contribute to all phases of the research process, from question formulation and…
Comparative Effectiveness Research
Comparative effectiveness research (CER) is the generation and synthesis of evidence that compares the benefits and harms of two or more prevention, diagnostic, or treatment options as they are used in routine clinical practice, with a focus on real world…
Comparative Study
A comparative study is any research design that compares two or more groups, interventions, conditions, or time periods to identify similarities and differences in outcomes, characteristics, or processes.
Complete Case Analysis
Complete case analysis, also called listwise deletion, is a statistical approach that includes only participants who have complete data for all variables of interest in the analysis, excluding anyone with any missing values.
Composite Endpoint
A composite endpoint is a single outcome measure that combines multiple individual clinical endpoints into one, used in clinical trials to increase the statistical event rate and reduce the required sample size.
Conceptual Framework
A conceptual framework is a visual or written representation of the key variables, constructs, and their expected relationships in a study.
Concurrent Validity
Concurrent validity is a type of criterion validity that evaluates how well a new measurement instrument agrees with an established gold standard when both are administered at the same point in time.
Confidence Interval
A confidence interval is a range of values, calculated from sample data by a method that, across repeated samples, captures the true population parameter at a specified rate called the confidence level.
Confirmability
Confirmability is one of the four criteria of trustworthiness in qualitative research, proposed by Lincoln and Guba as the qualitative counterpart to objectivity in quantitative inquiry.
Conflict of Interest
A conflict of interest in research occurs when a researcher's financial, personal, professional, or institutional interests could compromise, or reasonably appear to compromise, the integrity, objectivity, or ethical conduct of their work.
Confounding Variable
A confounding variable is an extraneous factor that is associated with both the independent variable and the dependent variable in a study, distorting the true relationship between the variables of interest by creating, exaggerating or masking an association.
Conjoint Analysis
Conjoint analysis is a survey based statistical technique used to understand how individuals value different attributes of a product, service, or intervention by presenting them with hypothetical scenarios that require trade offs.
Consensus Method
A consensus method is a structured approach for synthesizing expert opinions to address questions where published evidence is insufficient, conflicting, or absent.
CONSORT (Consolidated Standards of Reporting Trials)
CONSORT stands for Consolidated Standards of Reporting Trials, a reporting guideline designed to improve the transparency and completeness of published reports of randomized controlled trials.
Constant Comparative Method
The constant comparative method is a qualitative data analysis technique most closely associated with grounded theory, in which each piece of data is systematically compared with previously coded data throughout the analysis process.
Construct Validity
Construct validity refers to the degree to which a measurement instrument accurately captures the theoretical concept, or construct, it is intended to measure.
Content Analysis
Content analysis is a systematic research method for analyzing textual, visual, or audio material by identifying patterns, themes, or concepts within the data and, in its quantitative form, quantifying them.
Content Validity Index (CVI)
The Content Validity Index (CVI) is a quantitative measure of the extent to which the items on a measurement instrument are relevant to and representative of the construct they are intended to measure.
Continuous Data
Continuous data are numerical measurements that can take any value within a defined range and can theoretically be measured to any desired level of precision.
Control Group
A control group is the set of participants in an experimental study who receive either no intervention, a standard treatment, or a placebo, providing a baseline against which the effects of the experimental intervention are measured.
Convenience Sampling
Convenience sampling is a nonprobability sampling method in which participants are selected based on their accessibility and willingness to participate rather than through random selection from a defined population.
Convergent Validity
Convergent validity is a component of construct validity that provides evidence that measures of constructs expected to be related are, in fact, correlated in the direction theory predicts.
Conversation Analysis
Conversation analysis (CA) is a qualitative research method rooted in ethnomethodology and sociology that studies the structure, organization, and sequential patterns of naturally occurring talk in interaction.
Correlation
Correlation is a statistical measure that quantifies the degree and direction of the association between two variables.
Correlation Coefficient
A correlation coefficient is a numerical statistic that quantifies the strength and direction of the relationship between two variables on a standardized scale from negative 1 to positive 1: linear for Pearson's r, monotonic for rank based coefficients.
Cost Benefit Analysis (CBA)
Cost benefit analysis (CBA) is a form of full economic evaluation that compares the total costs of an intervention or program with its total benefits, with both costs and benefits measured in monetary terms.
Cost Consequence Analysis
Cost consequence analysis (CCA) is a form of economic evaluation that presents the costs and multiple outcomes of two or more alternatives in a disaggregated format, listing each cost and consequence separately without combining them into a single summary…
Cost Effectiveness Analysis (CEA)
Cost effectiveness analysis (CEA) is a form of full economic evaluation that compares the costs and health outcomes of two or more interventions, expressing results as an incremental cost effectiveness ratio (ICER): the difference in costs divided by the…
Cost Minimization Analysis
Cost minimization analysis (CMA) is a form of economic evaluation used when two or more interventions have been demonstrated to produce equivalent health outcomes, so that the evaluation reduces to a simple comparison of costs to identify the least expensive…
Cost of Illness Study
A cost of illness (COI) study estimates the total economic burden that a specific disease or health condition imposes on society, the health care system, patients, or payers.
Cost Per QALY
Cost per quality adjusted life year (QALY) is the incremental cost of an intervention divided by its incremental gain in QALYs compared with an alternative, serving as a standard measure of cost effectiveness in health care decision making.
Cost Utility Analysis (CUA)
Cost utility analysis (CUA) is a form of economic evaluation that compares the costs of health care interventions with their outcomes expressed in quality adjusted life years (QALYs), capturing both the quantity and quality of life in a single measure.
Cox Regression
Cox regression, also known as the Cox proportional hazards model, is a semiparametric statistical method used in survival analysis to examine the relationship between one or more predictor variables and the time to an event of interest (such as death,…
Credible Interval
A credible interval is the Bayesian counterpart to the frequentist confidence interval. It provides a range within which an unknown parameter falls with a specified posterior probability, given the observed data and a prior distribution.
Criterion Validity
Criterion validity is the degree to which scores from a measurement instrument correlate with an external criterion, an accepted measure of the same construct or an outcome it should predict.
Critical Appraisal
Critical appraisal is the systematic process of evaluating research evidence to assess its trustworthiness, methodological quality, and relevance to a specific clinical, policy, or research question.
Critical Discourse Analysis
Critical discourse analysis (CDA) is a qualitative research approach that examines how language is used in texts, speech, and other forms of communication to construct, reproduce, and challenge power relations, social identities, and ideological positions.
Critical Theory
Critical theory is a research paradigm and intellectual tradition concerned with power, inequality, and social justice, originating from the Frankfurt School of social thought in the 1930s (Max Horkheimer, Theodor Adorno, Herbert Marcuse, and later Jürgen…
Cronbach's Alpha
Cronbach's alpha is a statistical measure of the internal consistency reliability of a set of items in a psychometric instrument, such as a questionnaire, survey, or test.
Cross Case Analysis
Cross case analysis is a qualitative research technique used in multiple case study designs to examine themes, patterns, similarities, and differences across individual cases.
Cross Cultural Research
Cross cultural research is a systematic approach to comparing phenomena across different cultural groups, examining how cultural context shapes behaviors, beliefs, attitudes, or outcomes.
Cross Sectional Study
A cross sectional study is an observational design that examines a defined population at a single point in time or over a short period, measuring exposure and outcome simultaneously.
Crossover Trial
A crossover trial is a clinical trial design in which each participant receives both the experimental treatment and the control treatment in a predetermined sequence, usually separated by a washout period.
Crowdsourcing in Research
Crowdsourcing in research is the practice of distributing tasks to a large, often distributed group of people, typically through online platforms, to support activities such as data annotation, image classification, transcription, or distributed problem…
D
Data Anonymization
Data anonymization is the process of removing or transforming identifying information in research data so that individual participants cannot be re identified, even by the data holder or by combining the anonymized data with external sources.
Data Availability Statement
A data availability statement is a section in a published research article that describes where the underlying data supporting the study's findings can be accessed, what restrictions apply to access, and under what conditions the data may be reused.
Data Cleaning
Data cleaning is the process of detecting and correcting or removing inaccurate, incomplete, duplicate, or inconsistent entries from a dataset to improve its quality before analysis.
Data Collection
Data collection is the systematic process of gathering information from relevant sources to answer a research question, using methods selected to match the study design and the nature of the variables under investigation.
Data Curation
Data curation encompasses the management, processing, and enrichment of research data to produce well organized, thoroughly documented, and interoperable datasets suitable for analysis, sharing, and long term preservation.
Data Dictionary
A data dictionary is a centralized reference document that describes the structure, content, format, and meaning of each variable in a dataset.
Data Extraction
Data extraction in the context of evidence synthesis is the systematic process of collecting predefined information from each study included in a systematic review, using a standardized form or template.
Data Fabrication
Data fabrication is the intentional creation of data, results, or experimental observations that were never actually collected, measured, or observed, and their presentation as genuine research findings.
Data Harmonization
Data harmonization is the process of combining data from different sources and reorganizing them according to a unified schema so that the resulting dataset is internally consistent, comparable across its component sources, and suitable for pooled analysis.
Data Linkage
Data linkage is the process of combining records from two or more separately maintained data sources that relate to the same individual, event, or entity.
Data Mining
Data mining is the process of discovering patterns, correlations, anomalies, and meaningful structures in large datasets using statistical, mathematical, and computational techniques.
Data Paper
A data paper is a peer reviewed publication whose primary purpose is to describe a dataset in detail, including how it was collected, processed, formatted, and validated, without presenting a hypothesis driven analysis or drawing conclusions about the…
Data Privacy
Data privacy in research refers to the right of participants to control how their personal information is collected, stored, used, and shared within and beyond the research context.
Data Repository
A data repository is a digital archive where research datasets are deposited, preserved, curated, and made accessible for reuse by other researchers.
Data Safety Monitoring Board (DSMB)
A Data Safety Monitoring Board, also known as a Data Monitoring Committee (DMC), is an independent group of experts that monitors participant safety and treatment efficacy during the conduct of a clinical trial.
Data Saturation
Data saturation is the point in qualitative data collection at which no new themes, codes, categories, or substantive information emerge from additional interviews, observations, or other data sources.
Data Stewardship
Data stewardship is the responsible management and governance of research data throughout its entire lifecycle, from planning and collection through documentation, storage, analysis, sharing, and long term preservation.
Data Visualization
Data visualization is the graphical representation of data and information using visual elements such as charts, graphs, maps, diagrams, and infographics to communicate patterns, trends, relationships, and insights that might be difficult to perceive in raw…
Database
In research, a database is a structured collection of records or data organized for efficient search, retrieval, and management.
Deception in Research
Deception in research is the deliberate withholding of information from, or provision of misleading information to, research participants about some aspect of the study, including its purpose, procedures, or the nature of the stimuli being presented.
Decision Model
A decision model is a mathematical framework that structures a clinical, policy, or resource allocation decision by mapping out the possible pathways, their associated probabilities, costs, and outcomes.
Decision Tree
A decision tree is a graphical and mathematical model used in clinical decision analysis and health economics to represent a sequence of decisions and chance events, mapping out possible pathways and their associated probabilities, costs, and outcomes.
Delphi Method
The Delphi method is a structured consensus building technique that uses multiple rounds of questionnaires administered to a panel of experts, with controlled feedback between rounds, to converge toward group agreement on a topic where evidence is uncertain,…
Dependent Variable
The dependent variable is the variable in a research study whose value is expected to change in response to the manipulation or variation of one or more independent variables.
Descriptive Research
Descriptive research is a research approach that systematically observes and records the characteristics of a population, phenomenon, or situation without manipulating any variables.
Descriptive Statistics
Descriptive statistics are statistical methods used to summarize, organize, and describe the main features of a dataset without making inferences about the broader population from which the sample was drawn.
Design Control
Design control is a systematic, structured approach to managing the design and development process for medical devices, required in the US by FDA's Quality Management System Regulation (21 CFR 820) and set out in ISO 13485, to ensure that a finished device…
Design Validation
Design validation is the process of confirming that a medical device, as a finished product, meets user needs and its intended uses under actual or simulated use conditions.
Detection Bias
Detection bias refers to systematic differences between study groups in how outcomes are identified, measured, or assessed.
Diagnostic Accuracy
Diagnostic accuracy refers to the ability of a test to correctly identify the presence or absence of a target condition in comparison to a reference standard (often called the gold standard).
Diagnostic Test Accuracy Review
A diagnostic test accuracy (DTA) review is a specialized type of systematic review that evaluates the performance of one or more diagnostic tests by synthesizing data on sensitivity, specificity, and other accuracy metrics across multiple primary studies.
Diary Study
A diary study is a longitudinal research method in which participants record their experiences, behaviors, symptoms, moods, or activities in real time or near real time over a defined period, typically ranging from several days to several weeks.
Disability Adjusted Life Year (DALY)
The Disability Adjusted Life Year (DALY) is a composite measure of disease burden that expresses the total number of years of healthy life lost due to both premature mortality and disability. One DALY represents one year of healthy life lost.
Discount Rate
In health economic evaluations, the discount rate is the annual percentage rate at which future costs and health outcomes are reduced to their present value, reflecting the principle that people generally prefer benefits sooner rather than later and costs…
Discourse Analysis
Discourse analysis is a qualitative research method that examines how language is used in texts, conversations, and other communicative practices to construct meaning, identities, power relations, and social realities within specific contexts.
Discriminant Validity
Discriminant validity is a form of construct validity that provides evidence that measures of theoretically distinct constructs are empirically distinguishable from one another.
Distribution
In statistics, a distribution is a mathematical function or empirical description that shows all possible values of a variable and how frequently they occur.
DOI (Digital Object Identifier)
A Digital Object Identifier (DOI) is a unique, persistent alphanumeric string assigned to a digital object, most commonly a journal article, but also a dataset, report, conference paper, book chapter, or other scholarly output.
Dose Response
Dose response describes the relationship between the amount, intensity, or duration of an exposure (the "dose") and the magnitude of the resulting biological or clinical effect (the "response").
Double Blind
A double blind study is a research design in which neither the participants nor the researchers who interact with them, deliver the intervention, or assess the outcomes know which treatment group each participant has been assigned to.
Dual Reviewer Screening
Dual reviewer screening is a methodological safeguard in systematic reviews in which two independent reviewers assess each study for inclusion at both the title and abstract screening stage and the full text screening stage.
E
Ecological Study
An ecological study is an observational research design in which the unit of analysis is a group or population rather than an individual.
Economic Evaluation
An economic evaluation is a systematic, comparative analysis of the costs and consequences of two or more alternative health interventions, programs, or policies.
Economic Model
An economic model in health care is a simplified mathematical representation of a complex disease process, treatment pathway, or health care system used to estimate the costs and health outcomes of alternative interventions over time.
Effect Size
An effect size is a quantitative measure of the magnitude of a phenomenon, the strength of an association between variables, or the size of a difference between groups.
Effectiveness
Effectiveness refers to the ability of an intervention to produce its intended results when applied under routine, real world conditions, with diverse patient populations, variable adherence, and the complexities of everyday clinical practice.
Efficacy
Efficacy is the ability of an intervention to produce its intended results under ideal or carefully controlled conditions, such as those of a well designed randomized controlled trial.
Egger Test
The Egger test is a statistical method for detecting small study effects and potential publication bias in meta analysis.
Electronic Data Capture
Electronic data capture (EDC) is a computerized system designed for the collection, management, and storage of clinical research data, replacing traditional paper based case report forms with electronic forms that participants, research staff, or clinicians…
Empirical Research
Empirical research is research based on observed and measured phenomena, deriving knowledge from direct or indirect observation and experience rather than from theory, authority, or speculation alone.
Enrichment Design
An enrichment design is a clinical trial strategy that uses one or more preliminary steps to select patients in whom a treatment effect, if present, is more likely to be detected, then randomizes only those selected patients to receive the treatment or…
Equivalence Trial
An equivalence trial is a clinical trial designed to demonstrate that two treatments produce outcomes that are sufficiently similar, within a predefined margin of clinical acceptability, that neither is meaningfully inferior or superior to the other.
Ethnography
Ethnography is a qualitative research method rooted in anthropology that involves the immersive, sustained observation of a social group, community, or cultural setting to understand its behaviors, beliefs, social dynamics, and meaning making processes from…
EUDAMED (European Database on Medical Devices)
EUDAMED (European Database on Medical Devices) is a centralized information technology system established by the European Union under the Medical Device Regulation (EU 2017/745) and the In Vitro Diagnostic Regulation (EU 2017/746).
Evidence Based Medicine (EBM)
Evidence based medicine (EBM) is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.
Evidence Based Practice (EBP)
Evidence based practice (EBP) is the integration of the best available research evidence with professional expertise and the values and preferences of the individuals being served, to guide decisions in clinical, educational, social, and organizational…
Evidence Synthesis
Evidence synthesis is the process of systematically identifying, evaluating, and combining findings from multiple individual studies to draw broader, more reliable conclusions than any single study can provide.
Evidence to Decision Framework
An evidence to decision (EtD) framework is a structured approach used in guideline development to move from evidence appraisal to actionable recommendations by explicitly considering multiple criteria beyond the research evidence itself.
Ex Post Facto Research
Ex post facto research is a non experimental study design in which the researcher examines how an independent variable, one that has already occurred or cannot be manipulated, affects a dependent variable.
Exclusion Criteria
Exclusion criteria are the characteristics that disqualify a study or participant from being included in a research study or systematic review. These criteria are established before data collection begins and serve to create a well defined study population.
Exploratory Research
Exploratory research is a preliminary form of investigation conducted to clarify the nature of a problem, generate hypotheses, or identify variables for further study.
External Validity
External validity is the extent to which the results of a study can be generalized or applied to other settings, populations, time periods, or conditions beyond the specific context in which the study was conducted.
F
F Test
The F test is a statistical test that compares variances, for example to test whether group means differ significantly.
Face Validity
Face validity is the extent to which a test, survey, or measurement instrument appears, on its surface, to measure what it claims to measure.
Factor Analysis
Factor analysis is a statistical method that reduces a large number of observed variables to a smaller set of underlying factors or latent constructs by identifying patterns of correlation among the variables.
Factorial Design
A factorial design is an experimental design in which two or more independent variables (called factors) are manipulated simultaneously, allowing researchers to examine both the individual effects of each factor (main effects) and the combined effects of…
Feasibility Study
A feasibility study is a preliminary investigation conducted to evaluate whether a proposed research project, clinical trial, or intervention can be carried out as planned.
Field Study
A field study is a research investigation conducted in a natural, real world setting rather than in a laboratory or otherwise controlled environment.
Field Weighted Citation Impact (FWCI)
Field Weighted Citation Impact (FWCI) is a normalized citation metric that compares the number of citations a publication has received to the expected number of citations for publications of the same document type, publication year, and subject area.
Fisher Exact Test
The Fisher exact test is a statistical test used to determine whether there is a significant association between two categorical variables in a 2 x 2 contingency table.
Fixed Effect Model
A fixed effect model in meta analysis is a statistical approach that assumes all studies in the analysis are estimating a single common (fixed) treatment effect, and that any variation between study results is due solely to random sampling error.
Focus Group
A focus group is a qualitative research method in which a small group of participants (typically 4 to 12 people) engages in a guided discussion about a specific topic, led by a trained moderator.
Forest Plot
A forest plot is a graphical display used in meta analyses to present the results of individual studies and the overall pooled estimate in a single figure.
Formative Research
Formative research is investigation conducted during the development phase of an intervention, program, or policy to inform its design, refine its components, and identify potential barriers to implementation.
Framework Analysis
Framework analysis is a systematic approach to qualitative data analysis that uses a structured matrix (a "framework") to organize and interpret data according to key themes and cases.
Frequency Distribution
A frequency distribution is a summary of how often each value or category (or range of values) occurs in a dataset. It can be presented as a table, histogram, bar chart, or frequency polygon.
Full Text Screening
Full text screening is the stage in a systematic review where the complete texts of potentially relevant studies, identified during title and abstract screening, are retrieved and read in full.
Funnel Plot
A funnel plot is a graphical tool used in meta analyses to visually assess whether publication bias or other small study effects may be present.
Funnel Plot Asymmetry
Funnel plot asymmetry refers to a systematic departure from the expected symmetrical inverted funnel shape when study effect estimates are plotted against their precision in a meta analysis.
Futility Analysis
Futility analysis is a planned interim analysis conducted during a clinical trial to assess whether there is a sufficiently low probability that the trial will demonstrate a statistically significant treatment effect if it continues to completion.
G
GDPR in Research
GDPR in research refers to the application of the European Union's General Data Protection Regulation (Regulation 2016/679) to research activities.
Generalizability
Generalizability is the extent to which findings from a specific study can be applied to the broader target population, other settings, other time periods, or other conditions beyond those directly examined.
Generalized Estimating Equations (GEE)
Generalized Estimating Equations (GEE) is a statistical method for analyzing correlated or clustered data, such as repeated measurements on the same individuals over time, observations nested within groups (schools, clinics, families), or multi site studies.
Generalized Linear Model
A generalized linear model (GLM) is a flexible extension of ordinary linear regression that accommodates dependent variables following non normal distributions from the exponential family, including binomial, Poisson, gamma, and negative binomial…
Good Clinical Practice (GCP)
Good Clinical Practice (GCP) is an international ethical and scientific quality standard for the design, conduct, recording, and reporting of clinical trials that involve human participants.
Good Research Practice
Good Research Practice (GRP) is a set of principles and standards governing the ethical and scientific quality of research across all disciplines.
GRADE (Grading of Recommendations Assessment, Development and Evaluation)
GRADE is a systematic and transparent framework for rating the certainty (quality) of a body of evidence and for developing and presenting recommendations in health care.
Grey Literature
Grey literature refers to research and information produced by organizations outside of traditional commercial and academic publishing channels.
Grounded Theory
Grounded theory is a qualitative research methodology that generates theory systematically from data collected through observation, interviews, and documents, rather than testing a pre existing hypothesis.
H
h Index
The h index is a bibliometric indicator that measures both the productivity and citation impact of a researcher, group, or journal.
Hazard Analysis
Hazard analysis is a systematic process for identifying potential hazards associated with a product, process, or system, estimating the severity and probability of harm from each hazard, and determining appropriate risk control measures.
Hazard Ratio
The hazard ratio (HR) is a measure used in survival analysis that compares the rate at which events (such as death, disease recurrence, or hospitalization) occur in one group relative to another at any given point in time.
Helsinki Declaration
The Declaration of Helsinki is a statement of ethical principles for medical research involving human participants, adopted by the World Medical Association (WMA) in 1964 and revised multiple times since, most recently in October 2024.
HEOR (Health Economics and Outcomes Research)
Health Economics and Outcomes Research (HEOR) is a multidisciplinary field that evaluates the clinical, economic, and humanistic outcomes of health care interventions to inform decision making about resource allocation, pricing, reimbursement, and health…
Heterogeneity
Heterogeneity in the context of systematic reviews and meta analyses refers to the variability or differences among the results of individual studies included in the synthesis.
Hierarchical Linear Modeling (HLM)
Hierarchical Linear Modeling (HLM), also called multilevel modeling or mixed effects modeling, is a statistical method for analyzing data that have a nested or hierarchical structure, such as students within classrooms, patients within hospitals, or repeated…
Hierarchical Model
A hierarchical model, also called a multilevel model, is a statistical framework designed to handle data organized at multiple nested levels, such as patients within hospitals, students within schools, or repeated measurements within individuals.
HRQoL (Health Related Quality of Life)
Health related quality of life (HRQoL) refers to an individual's or group's perceived physical and mental health over time.
HTA (Health Technology Assessment)
Health technology assessment (HTA) is a multidisciplinary process that evaluates the medical, social, economic, and ethical implications of health technologies.
Human Subjects Research
Human subjects research is research that involves living individuals, either through intervention or interaction with them or through identifiable private information or biospecimens about them.
Hypothesis
A hypothesis is a testable, falsifiable statement that predicts the relationship between two or more variables.
Hypothesis Testing
Hypothesis testing is a formal statistical procedure that uses sample data to evaluate a claim about a population parameter.
I
I Squared (I²)
I squared (I²) is a statistic used in meta analysis to quantify the percentage of variability in effect estimates across studies that is attributable to true heterogeneity rather than sampling error.
ICER (Incremental Cost Effectiveness Ratio)
The incremental cost effectiveness ratio (ICER) is the ratio of the difference in costs between two health interventions to the difference in their health outcomes, most commonly measured in quality adjusted life years (QALYs).
Immortal Time Bias
Immortal time bias is a form of selection bias in observational studies that occurs when the period between cohort entry and the start of exposure includes a span of time during which the outcome of interest could not have occurred.
Impact Factor
The impact factor is a journal level metric that measures the average number of citations received per article published in a journal over a specific period.
Imputation
Imputation is a statistical technique for handling missing data by replacing absent values with estimated substitutes.
Incidence
Incidence is an epidemiological measure that quantifies the frequency of new cases of a disease, injury, or other health event arising within a defined population during a specified period.
Inclusion Criteria
Inclusion criteria are the predefined characteristics that a study participant, data source, or published study must possess to be eligible for enrollment in a research study or for selection in a systematic review.
Incremental Cost Effectiveness Ratio (ICER)
The incremental cost effectiveness ratio (ICER) is the ratio of the difference in costs to the difference in health outcomes between two interventions, typically expressed as the additional cost per quality adjusted life year (QALY) gained.
Independent Variable
The independent variable is the factor that is systematically manipulated, controlled, or measured by the researcher to examine its effect on the dependent variable.
Index Case
The index case is the first identified case of a disease or condition in a population or epidemiological investigation.
Indigenous Data Sovereignty
Indigenous data sovereignty is the principle that Indigenous peoples have the inherent right to govern the collection, ownership, access, and application of data about their communities, lands, cultures, and resources.
Individual Participant Data (IPD)
Individual participant data (IPD) refers to the raw, observation level data collected for each participant in a clinical study, as opposed to the aggregate summary statistics reported in published articles.
Inferential Statistics
Inferential statistics are methods that allow researchers to draw conclusions about a larger population based on data collected from a sample.
Informed Consent
Informed consent is the process by which a prospective research participant voluntarily agrees to take part in a study after receiving a thorough explanation of the study's purpose, procedures, potential risks and benefits, alternatives to participation, and…
Institutional Review Board (IRB)
An institutional review board (IRB) is an ethics committee, set up by a research institution or operating independently, that reviews, approves, and monitors research involving human subjects.
Intangible Costs
In health economics, intangible costs are the costs associated with pain, suffering, grief, loss of leisure, and diminished quality of life that are difficult to express in monetary terms.
Intention to Treat (ITT)
Intention to treat (ITT) is an analysis strategy in clinical trials that includes all randomized participants in the groups to which they were originally assigned, regardless of whether they adhered to the treatment protocol, completed the study, or received…
Inter Rater Reliability
Inter rater reliability is the degree of agreement between two or more independent assessors who evaluate, rate, or classify the same set of items, participants, or data.
Interim Analysis
An interim analysis is a planned examination of accumulating data conducted during the course of a clinical trial, before the study reaches its full enrollment or follow up target.
Internal Validity
Internal validity is the degree to which a study accurately establishes a causal relationship between the independent variable and the dependent variable, free from the influence of confounding variables, biases, or other systematic errors.
Interpretive Framework
An interpretive framework is the set of philosophical assumptions, beliefs, and theoretical perspectives that guide a qualitative researcher's approach to inquiry, shaping decisions about research design, data collection, analysis, and interpretation.
Intraclass Correlation Coefficient (ICC)
The intraclass correlation coefficient (ICC) is a measure of the degree of agreement or consistency among measurements made by multiple raters, across repeated measures of the same quantity, or between observations nested within groups.
J
Journal Impact Factor
The journal impact factor (JIF) is a metric calculated annually by Clarivate that measures the average number of citations received per article published in a specific journal during the two preceding years.
Judgmental Sampling
Judgmental sampling, also called purposive sampling, is a nonprobability sampling technique in which the researcher deliberately selects participants, cases, or units based on their own expertise and judgment about which selections will be most informative…
K
Kaplan Meier Estimate
The Kaplan Meier estimate is a nonparametric statistic used in survival analysis to estimate the probability of surviving (or remaining event free) beyond successive time points.
Kappa Statistic
The kappa statistic is a measure of inter rater agreement for categorical data that adjusts for the amount of agreement expected to occur by chance alone. Cohen's kappa applies to two raters, while Fleiss' kappa extends the measure to three or more raters.
Kruskal Wallis Test
The Kruskal Wallis test is a nonparametric statistical test used to determine whether there are statistically significant differences in the distributions (assessed through mean ranks) of a continuous or ordinal dependent variable across three or more…
L
Large Language Model (LLM)
A large language model (LLM) is a type of artificial intelligence system built on deep neural network architectures, typically transformers, trained on vast corpora of text data to generate, summarize, translate, and analyze natural language.
Level of Measurement
Level of measurement refers to the classification of variables into one of four hierarchical scales: nominal, ordinal, interval, and ratio.
Likert Scale
A Likert scale is a rating format commonly used in surveys and questionnaires that asks respondents to indicate their level of agreement, satisfaction, frequency, or intensity in response to a statement, typically using a five or seven point scale with…
Linear Regression
Linear regression is a statistical method that models the relationship between a continuous dependent variable and one or more independent variables by fitting a linear equation to the observed data.
Literature Review
A literature review is a comprehensive survey, critical analysis, and synthesis of existing published research on a specific topic.
Living Systematic Review
A living systematic review is a systematic review that is continually updated, incorporating new evidence as it becomes available rather than remaining a static document fixed at the time of publication.
Log Rank Test
The log rank test is a nonparametric statistical test used in survival analysis to compare the time to event distributions between two or more groups.
Logistic Regression
Logistic regression is a statistical method used to model the relationship between a binary dependent variable (one with two possible outcomes, such as disease present or absent) and one or more independent variables.
Longitudinal Study
A longitudinal study is a research design in which the same participants, groups, or populations are observed and measured repeatedly over an extended period of time.
M
Mann Whitney U Test
The Mann Whitney U test is a nonparametric statistical test that compares the distributions of a continuous or ordinal dependent variable between two independent groups.
Manuscript
A manuscript is the written document that presents the full account of a research study, prepared for submission to a scholarly journal for peer review and potential publication.
Margin of Error
The margin of error is a statistic expressing the amount of random sampling error in a survey's results.
Markov Model
A Markov model is a mathematical framework used primarily in health economics and decision analysis to simulate transitions between a set of discrete health states over time.
Maximum Likelihood Estimation
Maximum likelihood estimation (MLE) is a method for estimating the parameters of a statistical model by finding the values that maximize the likelihood function, which gives the probability (or probability density) of the collected data for specific…
Mean
The mean, or arithmetic average, is a measure of central tendency calculated by summing all values in a dataset and dividing by the number of values.
Measurement Error
Measurement error is the difference between a measured value and the true value of the quantity being measured.
Median
The median is the middle value in a dataset when all observations are arranged in ascending or descending order. If the number of observations is odd, the median is the central value; if even, it is the average of the two central values.
Meta Analysis
Meta analysis is a statistical method that combines the quantitative results of multiple independent studies addressing the same research question to produce a single, more precise summary estimate of the effect.
Meta Regression
Meta regression is a statistical extension of meta analysis that examines whether study level characteristics (covariates) explain variation in effect sizes across studies.
Methodological Quality
Methodological quality refers to the degree to which a study's design, conduct, and analysis minimize the risk of bias and support valid, reliable conclusions.
Missing Data
Missing data are observations or measurements that are absent from a dataset, arising from a variety of causes including participant dropout, nonresponse to survey items, equipment malfunction, data entry errors, or administrative gaps in record systems.
Mixed Model
A mixed model, also called a mixed effects model, is a statistical framework that contains both fixed effects (population level parameters that apply to the entire sample or population) and random effects (parameters that vary across groups, individuals, or…
Mode
The mode is the most frequently occurring value in a set of observations. A dataset can have one mode (unimodal), two modes (bimodal), or more (multimodal), and it is the only measure of central tendency applicable to nominal (categorical) data, where…
Multi Criteria Decision Analysis (MCDA)
Multi criteria decision analysis (MCDA) is a structured, transparent approach to decision making that evaluates alternatives against multiple criteria simultaneously.
Multicollinearity
Multicollinearity is a statistical condition that occurs when two or more independent variables in a regression model are highly correlated with each other.
Multiple Regression
Multiple regression is a statistical technique that models the relationship between a single dependent variable and two or more independent variables, allowing researchers to estimate the unique contribution of each predictor while controlling for the…
Multiple Testing Correction
Multiple testing correction refers to a set of statistical adjustments applied when multiple hypothesis tests are performed simultaneously.
Multivariate Analysis
Multivariate analysis encompasses a set of statistical methods designed to analyze data involving several variables jointly, typically more than one dependent variable, accounting for the relationships and correlations among them.
N
Narrative Review
A narrative review is a type of literature review that summarizes, synthesizes, and interprets a body of research on a specific topic using a qualitative, discursive approach rather than the formal, predefined search and appraisal methods used in systematic…
Narrative Synthesis
Narrative synthesis is a method of synthesizing findings from multiple studies using words, text, and structured reasoning rather than statistical pooling.
Negative Case Analysis
Negative case analysis is a strategy for enhancing the credibility and rigor of qualitative research by deliberately searching for and examining data, participants, or cases that do not fit the emerging patterns, themes, or theoretical explanations being…
Negative Predictive Value
The negative predictive value (NPV) is the probability that a person who receives a negative test result truly does not have the condition being tested for.
Network Meta Analysis
Network meta analysis (NMA), also known as mixed treatment comparison, is a statistical technique that simultaneously compares three or more interventions by combining both direct evidence (from head to head trials) and indirect evidence (inferred through a…
Non Probability Sampling
Non probability sampling is a sampling approach in which members of the population do not have a known, nonzero chance of being selected for the study.
Nonparametric Statistics
Nonparametric statistics are a class of statistical methods that do not assume the data follow a specific probability distribution, such as the normal distribution.
Normal Distribution
The normal distribution, also called the Gaussian distribution or bell curve, is a symmetric, continuous probability distribution defined by two parameters: the mean (mu) and the standard deviation (sigma).
Null Hypothesis
The null hypothesis (Hâ‚€) is the default proposition in statistical hypothesis testing that states there is no effect, no difference, or no association between variables.
Number Needed to Harm (NNH)
The number needed to harm (NNH) is the number of patients who need to be exposed to a risk factor, treatment, or intervention over a specific period before one additional patient experiences an adverse event that would not have occurred without the exposure.
Number Needed to Treat (NNT)
The number needed to treat (NNT) is the number of patients who need to be treated with a specific intervention for one additional patient to achieve a favorable outcome compared to the control or alternative treatment.
O
Observational Study
An observational study is a type of research design in which investigators observe participants without assigning treatments, exposures, or interventions.
Odds Ratio
The odds ratio (OR) is a measure of association that compares the odds of an event occurring in one group to the odds of it occurring in another group.
Open Access
Open access refers to the practice of making scholarly research publications freely available online so that anyone can read, download, copy, distribute, and use them without financial, legal, or technical barriers.
Open Label Study
An open label study is a clinical trial design in which both the investigators and the participants know which treatment each participant is receiving.
Open Peer Review
Open peer review is a model of scholarly peer review in which one or more elements of the traditional review process are made transparent rather than anonymous.
Operationalization
Operationalization is the process of defining a concept or construct in terms of specific, measurable, and observable indicators or procedures that can be used to detect and quantify it in research.
ORCID (Open Researcher and Contributor ID)
ORCID (Open Researcher and Contributor ID) is a unique, persistent digital identifier assigned to individual researchers and scholars.
Outlier
An outlier is a data point that falls far outside the overall pattern of a dataset, differing markedly from the other observations.
Overview of Reviews
An overview of reviews, sometimes called an umbrella review, is a type of evidence synthesis that systematically compiles and summarizes the findings of multiple systematic reviews on a related topic or set of interventions.
P
p Value
The p value is the probability of obtaining a result at least as extreme as the one observed in a study, assuming that the null hypothesis is true.
Paradigm
A paradigm is a broad framework of assumptions, concepts, values, and practices that constitutes a way of viewing reality for the community that shares it.
Parametric Statistics
Parametric statistics are a class of statistical methods that make specific assumptions about the distribution of the underlying population from which the data are drawn, most commonly that the data follow a normal (Gaussian) distribution.
Participant Observation
Participant observation is a qualitative research method in which the researcher immerses themselves in a social setting or community, participating in its activities while simultaneously observing and recording behavior, interactions, and cultural practices.
Path Analysis
Path analysis is a statistical method used to examine the directed relationships among a set of variables according to a hypothesized causal model.
Patient Reported Outcome (PRO)
A patient reported outcome (PRO) is any report of the status of a patient's health condition or treatment experience that comes directly from the patient, without interpretation by a clinician or anyone else.
Pearson Correlation
The Pearson correlation coefficient (r) is a measure of the strength and direction of the linear relationship between two continuous variables.
Peer Review
Peer review is the process by which scholarly work, typically a manuscript submitted to a journal, is evaluated by independent experts (peers) in the same field before publication.
Per Protocol Analysis
Per protocol analysis is a method of analyzing data from a clinical trial that includes only those participants who completed the study in full compliance with the protocol.
Performance Bias
Performance bias refers to systematic differences in the care provided to participants in a study, apart from the intervention being evaluated, that arise because participants, clinicians, or other providers know which treatment group a participant belongs…
Phase I Trial
A Phase I trial is the first stage of testing an experimental treatment in human subjects, primarily designed to evaluate the safety, tolerability, pharmacokinetics (how the body processes the drug), and pharmacodynamics (how the drug affects the body) of…
Phase II Trial
A Phase II trial is a clinical study that evaluates the efficacy and safety of an experimental treatment in patients with the target disease or condition.
Phase III Trial
A Phase III trial is a large scale, randomized, controlled clinical study designed to provide definitive evidence of the efficacy and safety of an experimental treatment compared to the current standard of care or placebo.
Phase IV Trial
A Phase IV trial, also called a post marketing study, is a clinical study conducted after a drug or other intervention has received regulatory approval and is available for clinical use.
Phenomenology
Phenomenology is a qualitative research approach rooted in philosophy that seeks to understand and describe the lived experience of individuals as they encounter a particular phenomenon.
PICO (Population, Intervention, Comparison, Outcome)
PICO is a framework used to formulate focused clinical and research questions by specifying four key components: the Population (who is being studied), the Intervention (what treatment or exposure is being examined), the Comparison (what alternative is being…
Pilot Study
A pilot study is a small scale, preliminary investigation conducted before a full scale study to test the feasibility, procedures, instruments, and methods that are planned for a larger project.
Placebo
A placebo is an inert or inactive treatment that is designed to resemble the experimental intervention in appearance, administration, and sensory characteristics but contains no active therapeutic ingredient.
PMCF (Post Market Clinical Follow Up)
Post Market Clinical Follow up (PMCF) is the systematic and ongoing process of collecting and evaluating clinical data on a medical device after it has been placed on the market and is in routine clinical use.
Point Estimate
A point estimate is a single numerical value derived from sample data that serves as the best estimate of an unknown population parameter.
Population
In research, a population is the entire group of individuals, objects, events, or measurements about which a researcher wishes to draw conclusions.
Positive Predictive Value
Positive predictive value (PPV) is the probability that a person who receives a positive test result truly has the condition being tested for.
Post Hoc Analysis
A post hoc analysis is any analysis conducted after data collection that was not specified in the original study protocol or statistical analysis plan.
Post Hoc Test
A post hoc test is a statistical procedure applied after an analysis of variance (ANOVA), usually one that yields a significant result, in order to identify which specific group means differ from one another.
Post Publication Review
Post publication review refers to the evaluation and critique of published research that occurs after publication, usually after formal peer review, through mechanisms such as commentary articles, letters to the editor, blog posts, social media discussions,…
Power (Statistical Power)
Statistical power is the probability that a study's statistical test will correctly detect a true effect when one exists, calculated as one minus the probability of a Type II error (beta).
Power Analysis
Power analysis is a statistical calculation performed during the planning stages of a study to determine the minimum sample size needed to detect an effect of a given magnitude with a specified level of confidence and statistical power.
Pre Post Design
A pre post design is a quasi experimental study design that measures an outcome before and after an intervention in a single group of participants, without including a concurrent control group.
Predatory Publishing
Predatory publishing is a business model in which publishers prioritize revenue generation over scholarly quality and integrity, often charging authors article processing fees while using deceptive practices and providing inadequate or nonexistent peer…
Prediction Interval
In meta analysis, a prediction interval is a range that estimates where the true effect in a new study drawn from the same population of studies would be expected to fall.
Predictive Modeling
Predictive modeling is the use of statistical algorithms or machine learning techniques to build a model that forecasts future outcomes or classifies observations based on patterns identified in historical data.
Predictive Validity
Predictive validity is a form of criterion validity that evaluates how well scores on a measurement instrument forecast a future outcome or behavior.
Preprint
A preprint is a version of a research paper that is shared publicly before undergoing formal peer review and journal publication.
Prevalence
Prevalence is the proportion of a defined population that has a particular disease, condition, or characteristic at a specific point in time (point prevalence) or during a specified period (period prevalence).
Primary Outcome
The primary outcome is the main endpoint that a study is designed and statistically powered to evaluate, specified in the study protocol before data collection begins.
Principal Component Analysis (PCA)
Principal component analysis (PCA) is a dimensionality reduction technique that transforms a set of correlated variables into uncorrelated linear combinations called principal components, each capturing the most variance left by earlier ones, with the first…
PRISMA (Preferred Reporting Items for Systematic Reviews and Meta Analyses)
PRISMA is a reporting guideline that provides a standardized checklist and flow diagram for the transparent and complete reporting of systematic reviews and meta analyses.
PRISMA Flow Diagram
The PRISMA flow diagram is a standardized graphical representation that documents the number of records identified, screened, assessed for eligibility, and included or excluded at each stage of a systematic review.
Probabilistic Sensitivity Analysis (PSA)
Probabilistic sensitivity analysis is a method used in health economic evaluations that assigns probability distributions to uncertain model input parameters and runs the model many times (typically thousands of iterations via Monte Carlo simulation) to…
Probability Sampling
Probability sampling is a sampling method in which every member of the target population has a known, nonzero probability of being selected for the study.
Propensity Score
A propensity score is the estimated conditional probability that an individual receives a particular treatment given a set of observed baseline covariates.
Propensity Score Matching
Propensity score matching (PSM) is a statistical technique that pairs treated and untreated individuals who have similar estimated propensity scores, creating a matched sample in which the distribution of observed baseline covariates is balanced between…
Protocol
A protocol is a detailed, prespecified plan for conducting a research study or systematic review, written in advance of data collection to define the research question, study design, methods, eligibility criteria, data collection procedures, and statistical…
Publication Bias
Publication bias is the systematic tendency for studies with positive, statistically significant, or novel results to be published more frequently and more promptly than studies with null, negative, or inconclusive findings.
Q
QALY (Quality Adjusted Life Year)
A quality adjusted life year (QALY) is a measure of health outcome that combines both the quantity and quality of life into a single metric, used in health economics to evaluate and compare the value of medical interventions.
QUADAS 2 (Quality Assessment of Diagnostic Accuracy Studies)
QUADAS 2 is a structured quality assessment tool designed to evaluate the risk of bias and concerns about applicability in primary diagnostic accuracy studies included in systematic reviews.
Qualitative Research
Qualitative research is a research approach that collects and analyzes non numerical data, such as text, audio recordings, images, and observations, to understand the meanings, experiences, perspectives, and social processes underlying human behavior and…
Quality Assessment
Quality assessment is the evaluation of individual studies included in a systematic review for their methodological rigor, examining potential sources of bias, confounding, and reporting deficiencies that could affect the validity and reliability of their…
Quantitative Research
Quantitative research is a research approach that collects and analyzes numerical data using statistical methods to test hypotheses, measure variables, and examine relationships or differences among them.
Quasi Experimental Design
A quasi experimental design is a research design that shares features with true experimental designs, such as the manipulation of an independent variable, but does not use random assignment to allocate participants to treatment and control conditions.
Questionnaire
A questionnaire is a structured set of questions designed to collect standardized data from respondents in survey research.
R
Random Effects Model
A random effects model is a statistical framework used in meta analysis that assumes the true treatment effect varies across studies, rather than being identical.
Randomization
Randomization is the process of assigning study participants to different groups (such as treatment and control) using a chance mechanism, ensuring that each participant has a known, typically equal, probability of being placed in any group.
Randomized Controlled Trial (RCT)
A randomized controlled trial is an experimental study design in which participants are randomly assigned to receive either the intervention being tested or a control condition (such as placebo, standard treatment, or no treatment).
Rapid Review
A rapid review is a form of evidence synthesis that uses simplified or abbreviated systematic review methods to produce findings within a shorter timeframe, typically weeks to a few months rather than the one to two years a full systematic review often takes.
Real World Data (RWD)
Real world data refers to health data collected outside of conventional clinical trials, drawn from sources that reflect routine clinical practice, patient behavior, and healthcare system operations.
Real World Evidence (RWE)
Real world evidence is clinical evidence about the usage and potential benefits or risks of a medical product or intervention derived from the analysis of real world data collected outside of conventional randomized controlled trials.
Receiver Operating Characteristic (ROC) Curve
A receiver operating characteristic curve is a graphical plot that illustrates the diagnostic performance of a binary classification system across all possible decision thresholds by plotting the true positive rate (sensitivity) on the vertical axis against…
Regression Analysis
Regression analysis is a family of statistical methods used to model the relationship between one or more independent (predictor) variables and a dependent (outcome) variable.
Regression Coefficient
A regression coefficient is a numerical value in a regression equation that represents the estimated average change in the dependent variable for each one unit change in the corresponding independent variable, while holding all other variables in the model…
Regression Discontinuity
Regression discontinuity (RD) is a quasi experimental research design that estimates causal effects by exploiting a known threshold or cutoff on a continuous assignment variable that determines treatment eligibility.
Regression to the Mean
Regression to the mean is a statistical phenomenon in which extreme values on a first measurement tend to be closer to the population average on subsequent measurements, regardless of any intervention applied between the measurements.
Relative Risk (Risk Ratio)
Relative risk, also called the risk ratio, is the ratio of the probability of an event occurring in an exposed or treated group to the probability of the same event occurring in an unexposed or control group.
Relative Risk Reduction
Relative risk reduction (RRR) is the proportional decrease in the risk of an event in the treatment group compared to the control group, calculated as one minus the relative risk and typically expressed as a percentage.
Reliability
Reliability is the degree to which a measurement instrument yields consistent, stable, and reproducible results when administered under the same conditions. It reflects the extent to which observed scores are free from random measurement error.
Replication
Replication is the process of repeating a study using similar or identical methods to determine whether the original findings can be reproduced. Direct replication uses the same methods, procedures, and conditions as the original study.
Reporting Bias
Reporting bias refers to systematic differences between reported and unreported research findings, encompassing both selective reporting of outcomes within individual studies and selective publication of entire studies based on the nature or direction of…
Research Design
Research design is the overall strategy, framework, and structure that a researcher uses to address a research question, encompassing the type of study (experimental, observational, or qualitative), the data collection methods, the sampling approach, and the…
Research Ethics
Research ethics encompasses the principles, standards, and practices that govern the responsible conduct of research, ensuring the protection of human participants, the integrity of the scientific record, and the responsible use of research resources.
Research Gap
A research gap is an area within the existing body of literature where knowledge is incomplete, contradictory, outdated, or entirely absent, indicating that further investigation is needed.
Research Question
A research question is a clear, focused, and answerable question that defines the purpose and direction of a study, determining its design, methodology, data collection, and analysis.
Research Synthesis
Research synthesis is the process of combining, analyzing, and interpreting findings from multiple individual studies on a particular topic to produce a comprehensive understanding that transcends what any single study can provide.
Research Waste
Research waste refers to the expenditure of scientific resources on studies that fail to produce usable, accessible, or relevant knowledge due to problems in design, conduct, analysis, reporting, or dissemination.
Response Rate
Response rate is the proportion of individuals who complete a survey, questionnaire, or study invitation out of the number of eligible individuals in the sample.
Retraction
A retraction is a formal notice indicating that a published research article should no longer be considered a reliable contribution to the scholarly record.
Risk of Bias
Risk of bias refers to the likelihood that the design, conduct, or analysis of a study has introduced systematic errors that could lead to an inaccurate estimate of the true effect.
Risk of Bias Assessment
Risk of bias assessment is the structured, systematic evaluation of the potential for systematic errors in a study's design, conduct, analysis, or reporting that could lead to over or underestimation of the true effect.
S
Sample
A sample is a subset of individuals, observations, or data points selected from a larger population for the purpose of conducting a study.
Sample Size
Sample size is the number of participants, observations, or units included in a study.
Sampling Error
Sampling error is the difference between a statistic calculated from a sample and the true parameter of the population from which the sample was drawn.
Scoping Review
A scoping review is a type of evidence synthesis that systematically maps the key concepts, types of evidence, and gaps in research on a broad topic area.
Screening Test
A screening test is a procedure applied to an asymptomatic population to identify individuals who may have a disease, condition, or risk factor that warrants further diagnostic evaluation.
Search Strategy
A search strategy is a structured, documented plan for identifying relevant studies in bibliographic databases and other sources, specifying the databases to be searched, the search terms (including subject headings and free text words), the Boolean…
Secondary Outcome
A secondary outcome is a prespecified endpoint that provides supplementary information about the effects of an intervention beyond what the primary outcome captures.
Selection Bias
Selection bias is a systematic error that arises when the way participants enter or stay in a study distorts its estimate of an association or effect.
Semi Structured Interview
A semi structured interview is a qualitative data collection method in which the interviewer uses a prepared guide of open ended questions and topics while retaining the flexibility to probe deeper, follow unexpected leads, and adapt the conversation based…
Sensitivity
In diagnostic testing, sensitivity is the ability of a test to correctly identify individuals who have the condition, calculated as the number of true positives divided by the total number of individuals who actually have the condition (true positives plus…
Sensitivity Analysis
A sensitivity analysis is an analytical procedure that tests how the results of a study, model, or systematic review change when key assumptions, decisions, or parameters are varied.
Snowball Sampling
Snowball sampling is a nonprobability sampling method in which existing study participants recruit additional participants from their social networks, creating a chain of referrals that expands the sample.
Spearman Rank Correlation
Spearman rank correlation is a nonparametric measure of the strength and direction of the monotonic relationship between two variables, calculated using the ranks of the data rather than the raw values.
Specificity
In diagnostic testing, specificity is the ability of a test to correctly identify individuals who do not have the condition, calculated as the number of true negatives divided by the total number of individuals who truly do not have the condition (true…
Standard Deviation
Standard deviation is a measure of the dispersion or spread of values in a dataset around the mean.
Standard Error
The standard error is the standard deviation of the sampling distribution of a statistic, most commonly the sample mean. It quantifies the precision of a sample statistic as an estimate of the corresponding population parameter.
Statistical Significance
A result is statistically significant when its p value, the probability of obtaining data at least as extreme as those observed if the null hypothesis were true, falls below a threshold set in advance, typically 0.05.
Stratified Sampling
Stratified sampling is a probability sampling technique in which the target population is divided into mutually exclusive, exhaustive subgroups (strata) based on a characteristic relevant to the research question, and a random sample is drawn independently…
Subgroup Analysis
A subgroup analysis examines whether the effect of an intervention or exposure differs across specific subsets of participants, defined by baseline characteristics such as age, sex, disease severity, or comorbidities.
Superiority Trial
A superiority trial is a clinical trial designed to demonstrate that a new treatment produces better outcomes than an existing treatment, placebo, or no treatment by a statistically significant margin, ideally one large enough to be clinically meaningful.
Surrogate Endpoint
A surrogate endpoint is a biomarker or intermediate outcome used in clinical trials as a substitute for a clinically meaningful final endpoint such as survival, disease progression, or functional status.
Survival Analysis
Survival analysis is a collection of statistical methods designed to analyze time to event data, where the outcome of interest is the time elapsed until a specific event occurs, such as death, disease recurrence, treatment failure, or hospital discharge.
Synthesis Without Meta Analysis (SWiM)
Synthesis Without Meta Analysis, abbreviated SWiM, is a reporting guideline for systematic reviews of intervention effects that combine findings from multiple studies when statistical pooling through meta analysis is not feasible or appropriate.
Systematic Review
A systematic review is a rigorous, transparent, and reproducible research method that identifies, evaluates, and synthesizes all available evidence relevant to a clearly formulated research question.
T
T Test
A t test is a parametric statistical test used to determine whether there is a statistically significant difference between the means of two groups or between a sample mean and a known population value.
Test Retest Reliability
Test retest reliability is a measure of the consistency of a measurement instrument over time.
Thematic Analysis
Thematic analysis is a qualitative research method for identifying, analyzing, and reporting patterns (themes) within data.
Theoretical Framework
A theoretical framework is the system of concepts, theories, and assumptions that a researcher adopts to guide the design, analysis, and interpretation of a study.
Time Horizon
A time horizon is the period over which outcomes, costs, and consequences are assessed in a research study, particularly in health economic evaluations, clinical trials, and decision analytic models.
Transferability
Transferability is a criterion for evaluating qualitative research that refers to the extent to which findings from one study can be applied or have relevance to other settings, populations, or contexts.
Trial Registration
Trial registration is the practice of recording essential information about a clinical trial in a publicly accessible registry before participant enrollment begins.
Triangulation
Triangulation is a research strategy that uses multiple methods, data sources, investigators, or theories to study the same phenomenon, with the goal of enhancing the credibility and comprehensiveness of the findings.
Trustworthiness
Trustworthiness is the overarching framework for evaluating the quality and rigor of qualitative research, analogous to the concepts of validity and reliability in quantitative research.
Two Tailed Test
A two tailed test is a statistical hypothesis test in which the alternative hypothesis specifies that the parameter of interest differs from the null value in either direction, without specifying whether the difference is positive or negative.
Type I Error
A Type I error, also called a false positive, occurs when a statistical test incorrectly rejects a true null hypothesis, concluding that an effect or difference exists when it does not.
Type II Error
A Type II error, also called a false negative, occurs when a statistical test fails to reject a false null hypothesis, concluding that no effect or difference exists when one actually does.
U
V
Validity
Validity in research refers to the degree to which a study, measurement, or inference accurately reflects or measures what it is intended to measure or assess. Validity is not a single property but rather a multifaceted concept with several distinct types.
Value of Information Analysis
Value of information (VOI) analysis is a decision analytic framework used to quantify the expected value of reducing uncertainty by collecting additional data before making a decision.
Variable
A variable is any characteristic, property, or attribute that can take on different values or categories across observations, participants, or experimental conditions.
Variance
Variance is a statistical measure of the dispersion or spread of a set of values around their mean.
W
Washout Period
A washout period is a designated interval of time in a clinical trial during which participants discontinue a previous treatment and allow its effects to dissipate before beginning a new treatment or entering a study intervention phase.
Wilcoxon Signed Rank Test
The Wilcoxon signed rank test is a nonparametric statistical test used to compare two related samples or matched pairs when the assumption of normality required by the paired samples t test is not met.
Willingness to Pay
Willingness to pay (WTP) is the maximum monetary amount that an individual, organization, or society is willing to spend for a unit of health benefit, such as one quality adjusted life year (QALY) or one disability adjusted life year (DALY) averted.
X
Y
Yates Correction
Yates correction, also called Yates continuity correction, is an adjustment applied to the chi square test for independence when analyzing a 2x2 contingency table.
Youden Index
The Youden index, also called Youden's J statistic, is a single summary measure of a diagnostic test's overall discriminative ability.
Z
Z-Score
A z-score, also known as a standard score, is a dimensionless quantity that expresses how many standard deviations a data point lies above or below the mean of its distribution.
Zelen Design
The Zelen design, also known as randomized consent design or prerandomization design, is a clinical trial methodology in which participants are randomized to treatment groups before being asked for informed consent.
Zero-Inflated Model
A zero-inflated model is a statistical regression model designed for count data that contains more zeros than would be expected under a standard Poisson or negative binomial distribution.