How To Calculate Kruskal Wallis Test

Expert Guide to Kruskal-Wallis Test

Introduction & Importance

The Kruskal-Wallis test is a non-parametric alternative to one-way ANOVA, used to compare the medians of three or more groups. It’s crucial for making informed decisions when data doesn’t meet the assumptions of parametric tests.

How to Use This Calculator

1. Enter the median values for each group.
2. Click ‘Calculate’.
3. View the results and chart below.

Formula & Methodology

The Kruskal-Wallis test uses the following formula to calculate the test statistic (H):

H = (12/N * (K – N + 1)) * (∑(R_i²) – N * (N + 1)²/4)

Where: N = total number of observations, K = number of groups, R_i = rank of i-th observation.

Real-World Examples

Data & Statistics

Group	Median	Rank Sum

Expert Tips

• Kruskal-Wallis test is sensitive to outliers.
• Use post-hoc tests like Dunn’s test for multiple comparisons.

Interactive FAQ

What are the assumptions of Kruskal-Wallis test?

Independence of observations, random sampling, and similar variance across groups.

Learn more about Kruskal-Wallis test from an authoritative source.