Wilcoxon signed-rank test??

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Gerda
Posts: 3
Joined: Sun Nov 15, 2015 2:21 pm

Wilcoxon signed-rank test??

Postby Gerda » Sun Nov 15, 2015 2:34 pm

Hi,

I have non-normal distributed data from the same people from two different measurement times.
The paired t-test is not possible because it is not normally distributed, but when I ask SPSS to do a non-parametrical test it automatically selects the Wilcoxon signed rank test. The output tells me that the median of the differences between the two measurement times is not zero. Can I really report it like that? Is the median a correct form of significance testing...?
Sorry for my bad english and for the stupid question, but I can find the answer no where else :-(.
Thank you for answering.



Spss 22.0, Windows 8
GerineL
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Posts: 1477
Joined: Tue Jun 10, 2008 4:50 pm

Re: Wilcoxon signed-rank test??

Postby GerineL » Tue Nov 17, 2015 11:30 am

yes, it is correct. Instead of comparing the mean, like with a t-test, between two timepoints, you compare the rank of people within groups. The centrality measure that accompanies that is indeed median.
look at some youtube clips about the test to get a better understanding, for instance, https://www.youtube.com/watch?v=mbpGCxYya3M
Gerda
Posts: 3
Joined: Sun Nov 15, 2015 2:21 pm

Re: Wilcoxon signed-rank test??

Postby Gerda » Tue Nov 24, 2015 3:38 pm

Thank you!

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