What does a significant Mann-Whitney test show?

The Mann-Whitney U test is used to compare whether there is a difference in the dependent variable for two independent groups. It compares whether the distribution of the dependent variable is the same for the two groups and therefore from the same population.

What do I report with Mann-Whitney U test?

In reporting the results of a Mann–Whitney test, it is important to state:

A measure of the central tendencies of the two groups (means or medians; since the Mann–Whitney is an ordinal test, medians are usually recommended)
The value of U.
The sample sizes.
The significance level.

Does Mann-Whitney U test compare means?

But since the Mann-Whitney test analyzes only the ranks, it does not see a substantial difference between the groups. The Mann-Whitney test compares the mean ranks — it does not compare medians and does not compare distributions.

How do you interpret Mann Whitney results in SPSS?

The Mann-Whitney test basically replaces all scores with their rank numbers: 1, 2, 3 through 18 for 18 cases. Higher scores get higher rank numbers. If our grouping variable (gender) doesn’t affect our ratings, then the mean ranks should be roughly equal for men and women.

What is the Mann Whitney U value?

The Mann-Whitney test statistic “U” reflects the difference between the two rank totals. The SMALLER it is (taking into account how many participants you have in each group) then the less likely it is to have occurred by chance.

What is the null hypothesis for the Mann-Whitney U test?

The null hypothesis for the test is that the probability is 50% that a randomly drawn member of the first population will exceed a member of the second population. Another option for the null hypothesis is that the two samples come from the same population (i.e. that they both have the same median).

How do you find the P value for Mann-Whitney U test?

6. Use statistical tables for the Mann-Whitney U test to find the probability of ob- serving a value of U or lower. If the test is one-sided, this is your p-value; if the test is a two-sided test, double this probabililty to obtain the p-value. 12 , where N = nx + ny.

Is the Mann Whitney U test the same as independent samples?

This would be more in keeping with the Mann-Whitney U test being used as an alternative to the independent-samples t-test (i.e., both would then use a measure of central tendency: the ‘mean’ for the independent-samples t-test and the ‘median’ for the Mann-Whitney U test).

Why does the Mann Whitney test not always achieve the confidence interval?

The Mann-Whitney test does not always achieve the confidence interval that you specify because the Mann-Whitney statistic (W) is discrete. Minitab calculates the closest achievable confidence level.

What is the critical value of Mann Whitney U?

Using n1 = 8 and n2 = 7 with a significance level of .01, the Mann-Whitney U Table tells us that the critical value is 6: Since our test statistic (12) is greater than our critical value (6), we fail to reject the null hypothesis. 5. Interpret the results.

Which is the alternative to the 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. Unlike the independent-samples t-test, the Mann-Whitney U test allows you to draw different conclusions about your data depending on the assumptions you make about your data’s distribution.

What does a significant Mann-Whitney test show?