American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What type of data is analyzed using the Mann-Whitney U-test?

1. Nominal, un-ordered categories

2. Normal, continuous data

3. Skewed, continuous or ordinal data

4. Ordinal data

The correct answer is: Skewed, continuous or ordinal data

The Mann-Whitney U-test is specifically designed for analyzing skewed continuous data or ordinal data. This non-parametric test does not assume that the data follows a normal distribution, which makes it particularly useful when dealing with datasets that may violate parametric assumptions. In practice, this means the test can be applied to two independent samples that either consist of ranks (ordinal) or continuous data that do not conform to a normal distribution. It examines whether there is a significant difference in the distributions of the two groups, making it an effective choice for situations where the sample sizes are small or the data characteristics are unknown. Choosing this test helps researchers derive meaningful insights from data that may be non-normally distributed or in ranked form, as opposed to methods that require data to be normally distributed and continuous. Thus, when the data is skewed or ordinal, the Mann-Whitney U-test is the appropriate statistical method to utilize.