Nonparametric Tests Guide

A skill for selecting and applying nonparametric statistical tests when data violate parametric assumptions. Covers rank-based tests for group comparisons, correlation, and paired data, with implementation examples and guidance on reporting.

When to Use Nonparametric Tests

Decision Criteria

Use nonparametric tests when:
  - Data are ordinal (Likert scales, rankings)
  - Distribution is clearly non-normal (heavy skew, outliers)
  - Sample size is very small (n < 15-20 per group)
  - Homogeneity of variance is violated
  - You are analyzing ranks or medians rather than means