Power Analysis Calculator
Two-sample mean (Z) • Power or required n • Ajax loading • Hard reset
Settings
Use “Compute Power” if you already know sample size. Use “Required Sample Size” to plan an experiment.
Two-sided detects changes in either direction. One-sided (upper) tests Δ > 0.
Quick summary
Enter inputs to compute power analysis.
Inputs
Used only in “Compute Power” mode. Total sample size ≈ 2n.
Default 0.05 if blank. Must be between 0 and 1.
Outcome variability (assumed equal across groups).
Difference in means you want to detect (Group B − Group A). Use a positive value.
Only used in “Required Sample Size” mode. Default 200000.
Results
Power (1-β)
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Required n per group
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In “Compute Power” mode this shows “—”. Total ≈ 2n.
Key stats
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Shows z-crit and standardized effect μ = Δ/SE.
Updating…
Action
Hard reset: cancels pending updates and clears everything on the first click.