Sample Size & Power

Sample Size & Power is a fast, fully offline study-planning tool. Pick the effect size you'd care about, your false-alarm rate, and the power you want - it tells you exactly how many subjects you need, then shows the power you'd get at any sample size. Too few subjects and a real effect slips by unnoticed. Too many wastes time and money. Power analysis finds the sweet spot before you collect a single data point. WHAT'S INSIDE Plan Set the effect size, alpha, target power, and one/two-sample or one/two-tailed - get the required n, total subjects, and the power at your own sample size instantly. Power The power curve (power vs n, with your target line and required-n marker), the null-vs-real overlap diagram, and the sample-size-vs-effect-size trade-off. Idea A plain-English walkthrough of why studies need enough subjects - effect size, alpha, power, and the two kinds of errors - with formulas rendered in offline KaTeX. Sim Drag effect size and n and watch the curves pull apart and the power change live. Send your settings straight to the Plan tab. Cases Worked study-planning examples - a drug trial, a teaching method, a before-and-after design - that load with one tap. WHY SAMPLE SIZE & POWER - 100% offline - your data never leaves your device - No account, no sign-up, no clutter - A distinctive gauge/speedometer-needle navigation, built just for this app - Required n, achieved power, and the full trade-off - not just one number - Input is never lost - your design is saved automatically Whether you're a student learning why power analysis matters, a researcher planning a real study, or just curious how many subjects an experiment actually needs, Sample Size & Power gives you the answer before you start collecting data.