Sample Size Calculator

Calculate required sample size for epidemiologic studies

Power Analysis

Study Parameters

Specify study design and statistical requirements

Study Design

Alpha (Type I Error)

Power (1 - β)

Detectable Risk Ratio

Minimum effect you want to detect

Baseline Risk

Allocation Ratio (Unexposed:Exposed)

Enter parameters and click calculate to see results

Key Considerations

Cohort/RCT: Based on comparing two proportions

Case-Control: Uses Schlesselman's formula

Power: 80% is standard, 90% for confirmatory studies