Hey people... if you give a detailed answer that makes sense, ill give u 10 points... i need help!?

Question

My question is based on psychology. I am doing my Mann-Witney U test, and I really need help on the ranking bit. I have a set of results which are 3 which are the same, what do i do?

Answer 1

Try this: (but if the results are truly identical, no test is needed!)

For small samples a direct method is recommended. It is very quick, and gives an insight into the meaning of the U statistic.

Choose the sample for which the ranks seem to be smaller (the smaller sample; the choice is relevant only to ease of computation). Call this "sample 1", and call the other sample "sample 2".
Taking each observation in sample 1, count the number of observations in sample 2 that are smaller than it.
The total of these counts is U.


EXAMPLE:

Suppose that Aesop is dissatisfied with his classic experiment in which one tortoise was found to beat one hare in a race, and decides to carry out a significance test to discover whether the results could be extended to tortoises and hares in general. He collects a sample of 6 tortoises and 6 hares, and makes them all run his race. The order in which they reach the finishing post is as follows, writing T for a tortoise and H for a hare:

T H H H H H T T T T T H
(his original tortoise still goes at warp speed, and his original hare is still lazy, but the others run truer to stereotype). What is the value of U?

Using the direct method, we take each tortoise in turn, and count the number of hares it beats, getting 6, 1, 1, 1, 1, 1. So U = 6 + 1 + 1 + 1 + 1 + 1 = 11.
Using the indirect method:
the sum of the ranks achieved by the tortoises is 1 + 7 + 8 + 9 + 1 0 + 11 = 46.
Therefore U = 6×6 + 6×7/2 − 46 = 36 + 21 − 46 = 11.
Consulting the table referenced below, we find that this result does not confirm the greater speed of tortoises, though nor does it show any significant speed advantage for hares. Note that a statistical package will give the same result.

http://www.google.com/url?sa=t&ct=res&cd=2&url=http%3A//fsweb.berry.edu/academic/education/vbissonnette/tables/mwu.pdf&ei=kc4VRPPrNYmiaJHcmdsG&sig2=BDlYpRrdGouLQHYVksJezg

Answer 2

I would simply rank the numbers at the same value and then skip the next 2 numbers in the ranking sequence, e.g. if those 3 are ranked as no.4, then the next ranking value would be 7.

Answer 3

the number 2

Answer 4

If values are same, anyone is unable to rank them by any test.......... means there is no effect of treatment
if values are different either this difference is greater or small then you can apply a range of tests like Tukey's, DMR, LSI, SNK tests etc

Answer 5

Take two of them away