This calculator uses a number of different equations to determine the minimum number of subjects that need to be enrolled in a study in order to have sufficient statistical power to detect a treatment effect.^{1}
Before a study is conducted, investigators need to determine how many subjects should be included. By enrolling too few subjects, a study may not have enough statistical power to detect a difference (type II error). Enrolling too many patients can be unnecessarily costly or time-consuming.
Generally speaking, statistical power is determined by the following variables:
To calculate the post-hoc statistical power of an existing trial, please visit the post-hoc power analysis calculator.
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