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Minimum Detectable Effect from Sample Size and Alpha Calculator

Smallest effect size detectable at given power and n.

Calculates the minimum detectable effect MDE = (z_α + z_β) × √(2σ²/n), where z_α is the critical value and z_β corresponds to desired statistical power (1−β).

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

MDE = (z_α + z_β) × √(2σ²/n)

In depth

Calculates the minimum detectable effect MDE = (z_α + z_β) × √(2σ²/n), where z_α is the critical value and z_β corresponds to desired statistical power (1−β).