How to interpret data from Mann-Whitney U Test
So I am doing a research project and I was told to d
Makayla Boyd
Answered question
2022-06-12
How to interpret data from Mann-Whitney U Test So I am doing a research project and I was told to do the Mann Whitney U Test. The research is examining male and female work experiences by them ranking statements from 1-6 (1 being strongly agree and 7 being strongly disagree). The goal is to see if their is a difference in work experience between the two groups. Using an online calculator these were my results: Key: 1st group/2nd group Variable: Female/Male Observations: 720/936 Mean: 3.099/3.042 SD: 1.715/1.668 Mann-Whitney test / Two-tailed test: U 341978.5 U (standardized) 0.532 Expected value 336960 Variance (U) 89023289.87 p-value (Two-tailed) 0.595 alpha 0.05 So I have all this great data. The first part makes sense to me but the data in the second part I don't know how to read/analyze. Can somebody explain. Thank you!
Answer & Explanation
Ryan Newman
Beginner2022-06-13Added 26 answers
U = 341978.5 This is the value of the Mann-Whitney U statistic, which is defined as
Here, represents the response of the person in the first group, which are women, and is the response of the person in the second group, which are men. However, this definition could have X and Y reversed, so you might want to double check. U (standardized) 0.532 This is the standardized value of the U-statistic, equal to , where and are given below. This standardized value is approximately normally distributed with mean 0 and variance 1, so 0.532 is a z-score; the more extreme it is, the more evidence there is to support the hypothesis that the two groups differ in their responses. Expected value 336960 This is , where m=936 and n=720. Variance (U) 89023289.87 This is the sample variance of the U statistic,
where is the number of people sharing rank i, where your ranks range from 1 to k=7. p-value (Two-tailed) 0.595 This is the conditional probability that, given there is no difference between the two groups, you would obtain a sample that is at least as extreme as the one you observed. It is a measure of the plausibility of the data you observed, assuming the null is true. Therefore, the smaller this value, the more evidence there is to favor rejecting the null hypothesis. alpha 0.05 This is the predefined significance level of the test and is the maximum Type I error you are willing to accept--i.e., you wish to limit the probability of incorrectly rejecting the null hypothesis to be at most 5%. Since the p-value exceeds , you do not reject and your conclusion is that the data furnishes insufficient evidence to suggest the two groups responded differently to the survey.