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Table 1 “Rules of thumb for interpreting effect sizes”

From: Application of standardised effect sizes to hospital discharge outcomes for people with diabetes

Cohen’s d Phi Coefficent
Effect Size d value Effect Size d value
Very small 0.01 Negligible 0.00 to < 0.10
Small 0.2 Weak 0.10 to < 0.20
Medium 0.5 Moderate 0.20 to < 0.40
Large 0.8 Relatively strong 0.40 to < 0.60
Very large 1.2 Strong 0.60 to < 0.80
Huge 2 Very strong 0.80 to < 1.00