Power Analysis — Two-Sample t-Test

Find the sample size you need for a two-sample t-test. Drag the effect-size slider and watch the required n move.

Effect size (Cohen’s d)

Significance level α (two-sided)

Power (1 − β)

Calculating…

Power vs. sample size per group at your effect size and α. The marker shows your current design.

Assumption check

Two-sided, equal group sizes, normal approximation. Answer: how many subjects per group to have the chosen power of detecting the given effect size.

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