如何计算Cohen's d Effect Size

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Cohen's d is a standardised effect size for the difference between two group means, expressed in standard deviation units. d=0.2 is small; d=0.5 medium; d=0.8 large.

分步指南

1. 1d = (μ₁ − μ₂) / σ_pooled
2. 2σ_pooled = √((σ₁² + σ₂²)/2)
3. 3Larger d = more practically significant difference
4. 4Allows comparison across studies regardless of measurement scale

例题解析