power-analysis-guide

Installation
SKILL.md

Power Analysis Guide

Calculate appropriate sample sizes for your study using power analysis, understand effect sizes, and avoid underpowered or wastefully overpowered designs.

Core Concepts

The Four Parameters of Power Analysis

Every power analysis involves four interrelated quantities. Fix any three to solve for the fourth:

Parameter Symbol Definition Typical Value
Effect size d, r, f, etc. Magnitude of the phenomenon you expect to detect Varies by field
Significance level (alpha) alpha Probability of Type I error (false positive) 0.05
Statistical power (1 - beta) 1 - beta Probability of detecting a true effect 0.80 or 0.90
Sample size N Number of observations needed Solve for this

Error Types

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Apr 2, 2026