Effect Size
A measure of how strong a relationship or difference is in research. In personality science, effect sizes show how much a trait actually predicts real-world outcomes.
Effect size tells you whether a statistically significant finding actually matters in practice. A tiny effect can be "significant" with a large enough sample — but that doesn't mean it's meaningful.
Common measures: r (correlation coefficient) — 0.10 = small, 0.30 = medium, 0.50 = large. In personality science: Big Five Conscientiousness → job performance: r=0.20-0.30 (meaningful). MBTI type → job performance: r=0.10 (negligible). RIASEC congruence → job satisfaction: r=0.28 (meaningful).
When someone says "this personality test predicts success," always ask about effect size. JobCannon's tests are based on frameworks with medium-to-large effect sizes for career-relevant outcomes.