Cohen's d measures the standardized difference between two means: (M1 - M2) / pooled SD. Values around 0.2 are small, 0.5 medium, 0.8 large.

How is Hedges' g different from Cohen's d?

Hedges' g applies a bias correction factor to Cohen's d, especially recommended for small sample sizes (n < 20).

What does CLES (probability of superiority) mean?

CLES is the probability that a randomly selected person from Group 1 has a higher score than a randomly selected person from Group 2. It ranges from 0.5 (no effect) to 1 (complete separation).

⚡ Effect Size Calculator

Cohen's d · Hedges' g · Glass's Δ · CLES · Overlap

Group 1 (Mean)

Group 1 (SD)

Group 1 (n)

Group 2 (Mean)

Group 2 (SD)

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Cohen's d

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Hedges' g

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Glass's Δ

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CLES

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Overlap

Interpretation: Cohen's d ≈ 0.00 (negligible)

📖 FAQ

What is Cohen's d? Standardized difference: (M1−M2)/pooled SD. Small=0.2, Medium=0.5, Large=0.8.

How is Hedges' g different? It applies a bias correction to Cohen's d, better for small samples.

What does CLES mean? Probability that a random person from Group 1 exceeds Group 2. 0.5 = no effect.