Wilcoxon 'signrank' test zval is not calculating
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Hello everyone,
I have a matrix for statistical analysis.
I performed the normal distribution test with the shapiro wilks test and observed that the data in my hand were not normally distributed.
According to this matrix, I want to analyze the pre- and post-intervention data of 15 people with signrank. When I do this analysis, the zval value cannot be determined as output. I couldn't understand why this happened? If the zval value cannot be calculated, is there an alternative test you can recommend?
I attaced my code and examples of variables.
load('ExampleData.mat');
[p,h,stats]=signrank(Var11(:,1),Var11(:,2));
stats
1 Comment
Frederik Bergmann
on 24 Oct 2022
Same problem here. and I tried both methods ('exact' and 'approximate')
Accepted Answer
Star Strider
on 27 May 2022
The ‘zval’ is only returned when the 'method' is 'approximate'.
There is no statistical difference between the vectors:
[p,h,stats]=signrank(Var11(:,1),Var11(:,2), 'method','approximate')
p =
0.30029
h =
logical
0
stats =
struct with fields:
zval: -1.0358
signedrank: 36
.
8 Comments
Maria Lazzaroni
on 13 Mar 2024
but if I use the 'exact' result, can I use the z value that I find when running the function signrank with 'method' = 'approximate'?
I do not understand why Matlab does not return the z value when running signrank with the method 'exect'.
Thanks a lot for the help ;)
Star Strider
on 13 Mar 2024
No.
That’s probably because the 'exact' method doesn’t use the normal distribution to calculate the probability. (The documentation doesn’t go into detail about that or how it calculates the probability for the 'exact' method. The references at the end of that page probably provide those details. I don’t have free access to them.)
My pleasure!
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