Sample Size Calculators
Choose a calculator to determine the required sample size for your study.
Two-Sample T-Test
Compare means between two independent groups with equal or unequal variances.
Two Proportions (Chi-Square)
Compare proportions between two independent groups using chi-square or Fisher's exact test.
Paired T-Test
Compare paired or matched observations (before/after, crossover first period).
One-Sample Proportion
Test a single proportion against a known or hypothesized value.
Log-Rank Test (Survival)
Compare survival curves between two groups using Schoenfeld or Freedman methods.
Non-Inferiority (Means)
Demonstrate that a new treatment is not worse than standard by a pre-specified margin.
Non-Inferiority (Proportions)
Non-inferiority test for binary outcomes using Farrington-Manning method.
One-Way ANOVA
Compare means across three or more independent groups using F-test.
Correlation (Pearson)
Test whether a correlation coefficient is significantly different from zero or another value.
Cluster Randomized Trial
Account for intracluster correlation in group-randomized designs (schools, clinics).
2×2 Crossover Design
Two-period crossover where each subject receives both treatments sequentially.
McNemar's Test
Compare paired proportions (matched case-control, before/after binary outcomes).