Observed arrival · 2026-09-24
StatPower, a calculator that asks whether your study can answer the question
A free, browser-based planner estimates sample size, statistical power, or effect size for several common study designs.
○Open
⊠Login
$Paid
†Ads
✦Pretty
●Pro
◎Niche
◉Human
⚑Risk
ƒJS
- For
- Researchers planning sample sizes for common study designs
- Worth noticing
- It uses the exact noncentral t distribution for t-tests, Fisher’s z for correlations, and an arcsine approximation for proportions.
Field notes
The planner can solve for sample size, power, or effect size and presents a power curve alongside its result. Its stated assumptions include independent participants, two equal-sized groups, a continuous outcome, and a common variance for the described two-group calculation. The page cautions that clustering, repeated measures, unequal allocation, and other more complex designs need design-specific analysis.
Observed signals
Read the marks
Editorial observations of this landing page, not a rating.
○OpenPublic substance visible
✦PrettyNotable craft visible
●ProPolished or operationally mature
◎NicheUnusually specific use
One card from the complete issue