Research tools.
Plan your research with simple calculators and explicit assumptions.
Sample size calculator
Estimate how many participants your study may need.
Percentage change
Explore percent and percentage points with your own numbers.
Margin of error
Explore how sample size affects uncertainty.
Effect size
Explore the difference between two independent groups using Cohen’s d and Hedges’ g.
Multiple-testing adjustment
Compare Bonferroni and Holm adjustments for your p-values.