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  Post-hoc Statistical Power Calculator for Student's t-Test

This calculator will tell you the observed power for a one-tailed or two-tailed t-test study, given the observed alpha level, the observed effect size, and the total sample size.

Please supply the necessary parameters, and then click the 'Calculate' button.

Alpha Level: Also known as the p-value, probability, or type I error rate. By convention, this value should be less than or equal to 0.05 to claim statistical significance.
Observed Effect Size (Cohen's d): By convention, effect sizes of 0.2, 0.5, and 0.8 are considered small, medium, and large, respectively. To compute an effect size from group means and standard deviations, click here.
Total Sample Size: The total number of valid cases used in the analysis. For example, if your study utilized two groups of 50 subjects each, this value would be 100.

 
 
 
 
The Statistics Calculators index now contains 56 free statistics calculators.

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