Power Analysis Calculator
Calculate required sample size or statistical power for your study. Sample-size results show the smallest supported integer size that reaches the target under the selected model.
T-test power uses noncentral t distributions and the independent test assumes equal population variances. Correlation uses a Fisher-z normal approximation; proportions use a normal approximation without continuity correction. These approximations may be inaccurate for small samples or rare events. One-tailed power assumes the effect is in the prespecified direction.
Step 1: Select Statistical Test
Step 2: What Do You Want to Calculate?
Step 3: Enter Parameters
Results
Independent Samples T-Test
n per group = 64
Effect Size
0.500(Medium)
Alpha
0.05
Target Power
0.8
Achieved power at this sample size: 0.8015
Tails
Two-tailed
Interpretation
To detect a medium effect (Cohen's d = 0.5) with 80% power at the 0.05 significance level, you need 64 participants per group (128 total).
