Since the data was not normally distributed, so I went for non-parametric test equivalent to Independent samples t-test. The sample size of group A is 13 and B is 18. The value of Mann Whitney U is 0. The p value is 0.000. What does it mean to have U value of 0? Is this test applicable or not? Or should I use some other test?
"U = 0 " means that all your values in one sample are greater compared to all the values in the other sample. " p value =0.000 " means pValue
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maybe you could review the basics of MWW :
https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test
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whether the test can be applied or not does not depend on the result ...
(here, the key assumptions are independence and ordinal variable)
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U = 0 basically means that all your values in one sample are larger than all the values in the other, a very extreme situation where you can reject the null hypothesis that the samples have been drawn from the same distribution (even for relatively small samples as yours)
therefore the pValue = 0, which means that you have zero chance to draw a more extreme U when sampling from the null
(in theory, the pValue is the probability that you draw an equal or more extreme value, therefore the pValue cannot be exactly zero but "pValue = 0.000" must be understood as "pValue is smaller than 0.000")
remember that extreme U values for MWW are the smallest values !
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"U = 0 " means that all your values in one sample are greater compared to all the values in the other sample. " p value =0.000 " means pValue
Thank you for clearing my doubt too. As, I have also got U statistics value, 0. Now, Can I proceed for decision and interpret my results?
I am assuming you used SPSS. I am not sure what your experimental design is but in most cases when you obtain a p value of 0 then you report it as p
Hello everyone,
I have two related questions on Wilcoxon Signed Rank Tests.
I used a Wilcoxon Signed Rank Test for my research project. The spss value for the mean negative ranks was 28, while the corresponding one for the positive ranks was 0. How should I interpret these results?
(Negative Ranks = performance scores before teaching intervention – performance scores after teaching intervention) (Positive Ranks = performance scores after teaching intervention – performance scores before teaching intervention)
The second question is about the Z value. In my study I found Z = -6.46 (and Asymp. Sig (2 tailed)
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