The Other Half of the Story: Effect Size Analysis in Quantitative Research

Abstract

Effect size measures are a key complement to statistical significance testing when reporting quantitative research findings. The authors provide a rationale for use of effect size and specific tools and guidelines for interpretation of results.

Abstract

Statistical significance testing is the cornerstone of quantitative research, but studies that fail to report measures of effect size are potentially missing a robust part of the analysis. We provide a rationale for why effect size measures should be included in quantitative discipline-based education research. Examples from both biological and educational research demonstrate the utility of effect size for evaluating practical significance. We also provide details about some effect size indices that are paired with common statistical significance tests used in educational research and offer general suggestions for interpreting effect size measures. Finally, we discuss some inherent limitations of effect size measures and provide further recommendations about reporting confidence intervals.