Welcome!

Power and Sample Size .com

Free, Online, Easy-to-Use Power and Sample Size Calculators

no java applets, plugins, registration, or downloads ... just free

Go Straight to the Calculators »


Power? What Power?

Statistical power is a fundamental consideration when designing research experiments. It goes hand-in-hand with sample size. The formulas that our calculators use come from clinical trials, epidemiology, pharmacology, earth sciences, psychology, survey sampling ... basically every scientific discipline.

Learn More »

Validated

We take the time to compare our calculators' output to published results. Moreover, our computation code is open-source, mathematical formulas are given for each calculator, and we even provide R code for the adventurous. The validation examples are cited at the bottom of each calculator's page.

See Validations »

By Nerds, For Nerds

We are a group of analysts and researchers who design experiments, studies, and surveys on a regular basis. This site grew out of our own needs. We have benefited from the wealth of knowledge and tools available online. This is our own small way of giving back to the analytics community.

About This Site »