Spss Mann Whitney U. The dependent variable must be as least ordinally scaled. Higher scores get higher rank numbers.
The mann whitney u test is considered non parametric because the outcome is not measured at a continuous level. The reason you would perform a mann whitney u test over an independent t test is when the data is not normally distributed. A mann whitney u test sometimes called the wilcoxon rank sum test is used to compare the differences between two independent samples when the sample distributions are not normally distributed and the sample sizes are small n 30.
I describe how to run the analysis and interpret the output.
It is considered to be the nonparametric equivalent to the two sample independent t test. The mann whitney u test is often considered the nonparametric alternative to the independent t test although this is not always the case. 1 2 3 through 18 for 18 cases. The reason you would perform a mann whitney u test over an independent t test is when the data is not normally distributed.
