Tutorial · 6 min
How to use Power & Study Design
Sample size before you collect anything
Sample-size and power calculations for means, proportions, correlations and ANOVA, with a design wizard that suggests the right test for your question.
Before you start
- • Expected effect size
- • Alpha and target power
Steps
- 1
Open Sample Size & Study Design
Sidebar → Sample Size & Study Design.
- 2
Choose the calculator that matches your outcome
Means, proportions, ANOVA, survival, Poisson, non-parametric or equivalence — the wizard lists each with its assumptions.
- 3
Enter your assumptions
Validation warns when a value is outside the usual range and shows the recommended default for each field.
- 4
Read the power curves
Drag the marker to read power at any sample size or effect size, and overlay scenarios to compare assumptions.
- 5
Save and export
Save named scenarios, import them later, and export plots as PNG/SVG with the curve data as CSV.
Tips
- • Inflate the final number for expected attrition before you write it into a protocol.
Troubleshooting
The required N is enormous
The assumed effect size is probably too small or the variance too large. Sanity-check both against published studies.