Non parametric tests - Mann Whitney

Question 1

what is the criteria for Mann Whitney non parametric tests?

Answer 1

independent groups - meaning that the design is unrelated

level of measurement is ordinal (which are converted to ranks)

Question 2

why are Mann Whitney tests used?

Answer 2

to see if there is a difference

Question 3

What are the steps of a Mann Whitney non parametric test?

Answer 3

1st - set an alternative an d null hypothesis

2 - ranking the data - need to consider data from groups a and b

(the lowest number has a rank of 1, when two data items are the same add up the rank they would get and give the mean for the ranks)

3 - calculate the sum of the ranks for Group A (Ra) and Group B (Rb)

4 -calculate the value of U is now called Ua for Group A and the number of participants for Group A is Na

5- then use the formula

6) work out the calculated and critical value

Question 4

how do we know if the result is significant?

Answer 4

if the calculated value of U is less than the critical value - it is significant