What is statistical power?

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What is statistical power?

Statistical power is the probability that a study will detect an effect if there is one. It measures how likely you are to reject the null hypothesis when the alternative is true. This is exactly the idea described as the probability of correctly rejecting a false null hypothesis. Power equals one minus the probability of a Type II error (failing to detect a real effect). The other statements refer to different concepts: the probability of a Type I error is about falsely declaring an effect when none exists and is set by the significance level, while the idea of obtaining significant results by chance relates to p-values under the null. In design, you boost power by increasing sample size, increasing the true effect size (or reducing noise), and choosing an appropriate significance level.

Statistical power is the probability that a study will detect an effect if there is one. It measures how likely you are to reject the null hypothesis when the alternative is true. This is exactly the idea described as the probability of correctly rejecting a false null hypothesis. Power equals one minus the probability of a Type II error (failing to detect a real effect). The other statements refer to different concepts: the probability of a Type I error is about falsely declaring an effect when none exists and is set by the significance level, while the idea of obtaining significant results by chance relates to p-values under the null. In design, you boost power by increasing sample size, increasing the true effect size (or reducing noise), and choosing an appropriate significance level.

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