# Kruskal-Wallis Calculator Compare three or more independent groups with the nonparametric Kruskal-Wallis H test > Canonical page: https://elysiatools.com/en/tools/kruskal-wallis-calculator - **Category:** Math & Numbers - **Keywords:** kruskal wallis test, nonparametric, rank test, group comparison, p value, calculator ## Overview The Kruskal-Wallis Calculator is a statistical tool designed to compare three or more independent groups using a nonparametric rank-based test. It serves as a robust alternative to the one-way ANOVA when data does not meet normality assumptions, allowing researchers to determine if there are statistically significant differences between group medians. ## Inputs - **Group Data** (textarea): One group per line, e.g. Control: 8, 9, 6, 7 A: 12, 10, 11, 13 B: 14, 15, 13, 16 - **Alpha** (number) - **Decimal Places** (number) ## When to use - When comparing three or more independent groups with non-normally distributed data. - When your dependent variable is measured on an ordinal scale or contains significant outliers. - When the assumption of homogeneity of variance is violated in a standard parametric ANOVA. ## How it works - Input your raw data for each group, separating groups by lines and values by commas or spaces. - Set your significance level (alpha) and preferred decimal precision for the calculation results. - The tool ranks all observations across all groups and calculates the H-statistic based on the sum of ranks. - The calculator determines the p-value and indicates whether to reject the null hypothesis based on your alpha. ## Use cases - Comparing customer satisfaction scores across four different retail store locations. - Analyzing the effectiveness of three different medication dosages on patient recovery times. - Evaluating student performance across multiple teaching methods where test scores are skewed. ## Frequently asked questions ### What is the null hypothesis for the Kruskal-Wallis test? The null hypothesis states that the population medians of all groups are equal. ### How many groups can I compare with this tool? You can compare three or more independent groups; for exactly two groups, the Mann-Whitney U test is typically used. ### Does this tool perform post-hoc testing? No, this tool calculates the H-statistic and p-value for the overall group comparison only. ### What does a 'Reject Null: True' result mean? It indicates that there is a statistically significant difference between at least two of the groups at your chosen alpha level. ### Can I use this for paired or dependent data? No, the Kruskal-Wallis test is specifically designed for independent samples. 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