Increasing emphasis has been placed on the use of effect size reporting in the analysis of social science data. Nonetheless, the use of effect size reporting remains inconsistent, and interpretation of effect size estimates continues to be confused. Researchers are presented with numerous effect sizes estimate options, not all of which are appropriate for every research question. Clinicians also may have little guidance in the interpretation of effect sizes relevant for clinical practice. The current article provides a primer of effect size estimates for the social sciences. Common effect sizes estimates, their use, and interpretations are presented as a guide for researchers.

This article presents a number of commonly used and important effect size measures. It is worth noting that it is not possible to describe all effect size measures available as they are quite numerous. There are several resources to which the reader is referred for further discussion (e.g., Cohen 1992; Sapp, 2006). The current article is intended as an introductory primer for researchers who may not be familiar with the range of effect size estimates available to them, and when they should be used. No effect size measure is perfect for all situations, and some disagreement persists over the advantages of some over others. This article is intended as a general guideline. Ultimately, researchers are encouraged to select wisely (and conservatively) from among the options presented. Interpretation of effect sizes will always remain context specific. Accepting effect sizes of any magnitude as clinically or practically significant renders their usefulness as moot. Psychologists must be willing to objectively identify minute effects and interpret them as such. Only by being realistic will we know when we are actually on to something.

This article presents a number of commonly used and important effect size measures. It is worth noting that it is not possible to describe all effect size measures available as they are quite numerous. There are several resources to which the reader is referred for further discussion (e.g., Cohen 1992; Sapp, 2006).
The current article is intended as an introductory primer for researchers who may not be familiar with the range of effect size estimates available to them, and when they should be used. No effect size measure is perfect for all situations, and some disagreement persists over the advantages of some over others. This article is intended as a general guideline. Ultimately, researchers are encouraged to select wisely (and conservatively) from among the options presented. Interpretation of effect sizes will always remain context specific. Accepting effect sizes of any magnitude as clinically or practically significant renders their usefulness as moot. Psychologists must be willing to objectively identify minute effects and interpret them as such. Only by being realistic will we know when we are actually on to something.