# Mann-Whitney U Test Calculator Compare two independent samples with the nonparametric Mann-Whitney U rank-sum test > Canonical page: https://elysiatools.com/en/tools/mann-whitney-u-test-calculator - **Category:** Math & Numbers - **Keywords:** mann whitney u test, rank sum test, nonparametric, independent samples, p value, calculator ## Overview The Mann-Whitney U Test Calculator is a nonparametric statistical tool used to determine if there are significant differences between two independent groups. By comparing the ranks of data points rather than their raw values, this calculator provides a robust alternative to the independent t-test when data is not normally distributed or contains ordinal values. ## Inputs - **Group 1 Values** (textarea): e.g. 12, 15, 14, 18, 16 - **Group 2 Values** (textarea): e.g. 9, 11, 10, 13, 12 - **Alternative Hypothesis** (select) - **Alpha** (number) - **Decimal Places** (number) ## When to use - When comparing two independent groups where the data does not follow a normal distribution. - When your dependent variable is measured on an ordinal scale or contains significant outliers. - When sample sizes are small and the assumptions for a parametric t-test cannot be met. ## How it works - Input the numerical values for two independent groups into the respective text areas using comma or space separation. - Select your alternative hypothesis (two-sided, greater than, or less than) and set your significance level (alpha). - The tool ranks all observations from both groups combined and calculates the U statistic based on the sum of these ranks. - The calculator outputs the U and Z statistics, the p-value, and a clear indication of whether to reject the null hypothesis. ## Use cases - Comparing the test scores of students from two different teaching methods when scores are skewed. - Analyzing patient recovery times between a treatment group and a control group in a clinical study. - Evaluating customer satisfaction ratings between two different product versions using ordinal survey data. ## Frequently asked questions ### What is the difference between this and a t-test? The Mann-Whitney U test is nonparametric and compares ranks, while a t-test compares means and assumes a normal distribution. ### Can I use this for paired samples? No, this test is specifically for independent samples; use the Wilcoxon Signed-Rank test for paired or related data. ### What does a significant p-value indicate? A p-value less than your alpha suggests a statistically significant difference in the distribution of the two groups. ### How are ties handled in the ranking? The calculator assigns the average rank to tied values to ensure accurate U statistic computation. ### Is there a limit to the sample size? 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