Power calculationResearch

A pre-study estimate of how many participants are needed to reliably detect an effect.

A power calculation (or sample size calculation) is performed before a study begins to estimate the minimum number of participants needed to detect a true effect of a given size, given an assumed variability, significance threshold, and desired statistical power (conventionally 80%). It helps readers judge whether a study was adequately sized to find a real effect, or whether a non-significant result may simply reflect an underpowered study rather than a true absence of effect. The estimate depends on assumptions made in advance (expected effect size, variance) that may not hold in the actual data, so it is only as trustworthy as those inputs.

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This guide was auto-drafted and is pending editorial review.