Effect Size Interpretation Guide

Use

Use this when comparing groups.

Common Effect Ideas

• Mean difference: how many units apart two averages are.
• Proportion difference: how many percentage points apart two proportions are.
• Risk ratio: how many times as common one outcome is compared with another.
• Odds ratio: a comparison of odds, useful but easy to overread.

Careful Habit

Always ask whether the difference is large enough to matter in the real decision.