Mann-Whitney U Test in Statistics

Mann-Whitney U Test

• A non-parametric test used to determine whether there is a significant difference between the distributions of two independent groups.
• Also known as the Wilcoxon rank-sum test.
• Used to test whether two samples are likely to derive from the same population (i.e., that the two populations have the same shape).

Assumptions of Mann-Whitney U Test

• The variable being compared between the two groups must be continuous.
• The data are assumed to take a non-Normal, or skewed, distribution.
• The data are assumed to be similar in shape across the two groups.
• The data should be two randomly selected independent samples, meaning the groups have no relationship to each other.
• Sufficient sample size is needed for a valid test, usually more than 5 observations in each group.

Running Mann-Whitney U Test

• State the null hypothesis and alternate hypothesis.
• Formulate an analysis plan.
• Calculate the test statistic.
• Interpret your results.

Sample Scenarios

• Comparing customer satisfaction scores between two different store locations.
• Comparing student performance between two different teaching methods.

Example Problem

• A researcher wants to compare the effectiveness of two different teaching methods on student performance.
• The null hypothesis is that the effectiveness of the two teaching methods are the same.
• The alternative hypothesis is that the effectiveness of the two teaching methods are not the same.
• The test is run with a 95% level of confidence and a p-value significance level.

Understand the Mann-Whitney U test, a non-parametric test used to determine if there is a significant difference between the distributions of two independent groups.