Practical Significance:The Use of Effect Sizes in School Counseling Research

Abstract

In response to the increasing call by professional organizations, journal editors, and statisticians to include not only derived significance levels from quantitative statistical procedures but also measures of effect sizes (ES), this article first provides a rationale for school counseling-related researchers to include these key indices in their studies. We contend that with this information, readers are better able to contextualize and properly interpret research findings and conclusions. Second, the three major ES families and the indices associated with each one are reviewed. Next, the influence of various research designs and differing sample sizes on the size of these effects is discussed, followed by an introduction to ES computation, reporting, and interpretation, particularly as these issues relate to school counseling settings. Practical examples, ES summary tables, and supplementary resources are overviewed as well.