Study Design & Sample Size Helper
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About & Limitations

What this app does

This app helps clinicians and trainees estimate sample sizes for common study designs. It focuses on simplicity and plain language rather than comprehensive statistical coverage.

Who it's for

Internal medicine fellows, public health trainees, clinicians doing theses, and physicians with limited formal statistics training.

What it does NOT do

  • •It does not replace statistical consultation for complex designs.
  • •It does not handle cluster / multilevel / design-effect calculations.
  • •It does not support survival analysis, non-inferiority, or equivalence designs.
  • •It does not perform Bayesian sample size calculations.
  • •It does not store any patient data.

Predictor studies disclaimer

The predictor study path provides rough planning guidance based on simplified rules of thumb. It should not be treated as a definitive sample size calculation.

How share links work

Share links encode only the calculator type and your entered assumptions (e.g. proportions, alpha, power). They contain no patient or personal information.

References

  1. Fleiss JL, Levin B, Paik MC. Statistical Methods for Rates and Proportions. 3rd ed. Wiley; 2003.
  2. Chow SC, Shao J, Wang H, Lokhnygina Y. Sample Size Calculations in Clinical Research. 3rd ed. Chapman & Hall/CRC; 2018.
  3. Peduzzi P, Concato J, Kemper E, et al. A simulation study of the number of events per variable in logistic regression analysis. J Clin Epidemiol. 1996;49(12):1373-1379.
  4. Green SB. How many subjects does it take to do a regression analysis? Multivariate Behav Res. 1991;26(3):499-510.
  5. Abramowitz M, Stegun IA. Handbook of Mathematical Functions. Dover Publications; 1965.