Sample size & power
Plan a study and compare its assumptions.
Start from an example
Two independent means
Effect-size helpers
These transformations help express assumptions; they do not choose a scientifically meaningful effect for you.
The paired helper assumes equal SD at both occasions: SD(diff) = SD × √(2(1 − correlation)).
Methods, scope & privacy
Calculations run locally in R using pwr and stats. Each result records the method, approximation and assumptions. No dataset is required; plans stay in this tab until you download them.
General repeated-measures interactions, mixed models, adaptive trials and Bayesian assurance require different planning models and are outside this catalogue.
Numerical checks cover reference calculations, integer rounding, allocation, attrition and solver round trips. They do not establish that a study’s assumptions are appropriate.
Your planning result
Your result and sensitivity curve appear here once the local engine is ready.
Scenarios
Keep up to eight scenarios. Save a plan to reopen its assumptions later.
Keep a scenario to compare alternative assumptions.