Welcome to Open Power Samplesize

Learn the fundamentals of statistical power and sample size, crucial for research design. The formulas our calculators use come from a wide range of scientific disciplines—including clinical trials, epidemiology, psychology, and more—to ensure reliable and efficient study results.

Our calculations are based on trusted R code and the jStat library, and we validate our output against published results. For full transparency, our code is open-source, with mathematical formulas and R code provided for each calculator.

Zarathu goes beyond data analysis, partnering with researchers to create a more beautiful world. We provide custom data analysis applications, comprehensive research consulting from study design to publication, and R education, treating research as an art and researchers as fellow artists.