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- is the array of x values.
- is the array of y values.
- is the value between 0 and 1.
- is either TRUE or FALSE.
- This function gives the test statistic value of the Mann Whitey U test.
- It is one type of Non parametric test.It is also called Mann–Whitney–Wilcoxon,Wilcoxon rank-sum test or Wilcoxon–Mann–Whitney test.
- Using this test we can analyze rank-ordered data.
- This test is alternative to the independent-sample, Student t test, and yields results identical to those obtained from the Wilcoxon Two Independent Samples Test.
- This test is used to compare differences between two independent groups when the dependent variable is either ordinal or continuous, but not normally distributed.
- Mann whitey u test is having the following properties:
- 1.Data points should be independent from each other.
- 2.Data do not have to be normal and variances do not have to be equal.
- 3.All individuals must be selected at random from the population.
- 4.All individuals must have equal chance of being selected.
- 5.Sample sizes should be as equal as possible but for some differences are allowed.
- Suppose the two groups of the populations have distributions with the same shape it can be viewed as a comparison of two medians.With out the assumption the Mann-Whitney test does not compare medians.
- To find statistic value of this test the steps are required:
- 1.For the two observations of values, find the rank all together.
- 2.Add up all the ranks in a first observation.
- 3.Add up all the ranks in a second group.
- 4.Select the larger rank.
- 5.Calculate the number of participants,number of people in each group.
- 6.Calculate the test statistic:
- where and are number of participants and number of people.
- is the larger rank total. is the similar value of .
- 7.State Result: In this step we have to take a decision of null hypothesis either accept or reject depending on the z value using critical value table.
- 8.State Conclusion: To be significant, our obtained U has to be equal to or LESS than this critical value.
Mann Whitney U Test