I am running a pairwise wilcoxon signed rank test, and I am not sure how to interpret the result. I would like to see if there is a difference between the values in conditions a and b. It doesn't seem possible to have a V = 0, but a significant p value. Am I doing something wrong? The command I used is this: wilcox.test(x=a$x,y=b$x,paired=TRUE) The output looks like this: Wilcoxon signed rank test data: a$x and b$x V = 0, p-value = 0.0009766 alternative hypothesis: true location shift is not equal to 0 The raw data is here: a participant condition x 34 1 fused.mu.control 315.5677 35 2 fused.mu.control 516.8781 36 3 fused.mu.control 362.8108 37 4 fused.mu.control 482.6022 38 5 fused.mu.control 423.6593 39 6 fused.mu.control 404.9358 40 8 fused.mu.control 342.7314 41 9 fused.mu.control 466.7561 42 10 fused.mu.control 467.5002 43 11 fused.mu.control 434.0221 44 12 fused.mu.control 480.2990 b participant condition x 45 1 fused.multi 373.0648 46 2 fused.multi 517.5159 47 3 fused.multi 390.2658 48 4 fused.multi 497.2303 49 5 fused.multi 519.7867 50 6 fused.multi 499.7950 51 8 fused.multi 345.8077 52 9 fused.multi 479.1607 53 10 fused.multi 539.5856 54 11 fused.multi 446.9569 55 12 fused.multi 569.5171 -- View this message in context: http://r.789695.n4.nabble.com/Wilcoxon-V-0-tp4637675.html Sent from the R help mailing list archive at Nabble.com.
Wilcoxon V = 0
4 messages · Naomikb, David L Carlson, Peter Ehlers
It all depends on which order you put the values. Try this wilcox.test(x=b$x,y=a$x,paired=TRUE) Either one is an extreme. A non significant value would be in the middle. ---------------------------------------------- David L Carlson Associate Professor of Anthropology Texas A&M University College Station, TX 77843-4352
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- project.org] On Behalf Of Naomikb Sent: Tuesday, July 24, 2012 4:36 PM To: r-help at r-project.org Subject: [R] Wilcoxon V = 0 I am running a pairwise wilcoxon signed rank test, and I am not sure how to interpret the result. I would like to see if there is a difference between the values in conditions a and b. It doesn't seem possible to have a V = 0, but a significant p value. Am I doing something wrong? The command I used is this: wilcox.test(x=a$x,y=b$x,paired=TRUE) The output looks like this: Wilcoxon signed rank test data: a$x and b$x V = 0, p-value = 0.0009766 alternative hypothesis: true location shift is not equal to 0 The raw data is here: a participant condition x 34 1 fused.mu.control 315.5677 35 2 fused.mu.control 516.8781 36 3 fused.mu.control 362.8108 37 4 fused.mu.control 482.6022 38 5 fused.mu.control 423.6593 39 6 fused.mu.control 404.9358 40 8 fused.mu.control 342.7314 41 9 fused.mu.control 466.7561 42 10 fused.mu.control 467.5002 43 11 fused.mu.control 434.0221 44 12 fused.mu.control 480.2990 b participant condition x 45 1 fused.multi 373.0648 46 2 fused.multi 517.5159 47 3 fused.multi 390.2658 48 4 fused.multi 497.2303 49 5 fused.multi 519.7867 50 6 fused.multi 499.7950 51 8 fused.multi 345.8077 52 9 fused.multi 479.1607 53 10 fused.multi 539.5856 54 11 fused.multi 446.9569 55 12 fused.multi 569.5171 -- View this message in context: http://r.789695.n4.nabble.com/Wilcoxon-V- 0-tp4637675.html Sent from the R help mailing list archive at Nabble.com.
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On 2012-07-24 14:36, Naomikb wrote:
I am running a pairwise wilcoxon signed rank test, and I am not sure how to interpret the result. I would like to see if there is a difference between the values in conditions a and b. It doesn't seem possible to have a V = 0, but a significant p value. Am I doing something wrong?
Not understanding the test? V is the sum of the ranks[*] of those pairs for which a$x > b$x; there are none, so V = 0. You can check the p-value with the [dp]signedrank() function. [*] ranks of absolute differences. Peter Ehlers
The command I used is this:
wilcox.test(x=a$x,y=b$x,paired=TRUE)
The output looks like this:
Wilcoxon signed rank test
data: a$x and b$x
V = 0, p-value = 0.0009766
alternative hypothesis: true location shift is not equal to 0
The raw data is here:
a
participant condition x
34 1 fused.mu.control 315.5677
35 2 fused.mu.control 516.8781
36 3 fused.mu.control 362.8108
37 4 fused.mu.control 482.6022
38 5 fused.mu.control 423.6593
39 6 fused.mu.control 404.9358
40 8 fused.mu.control 342.7314
41 9 fused.mu.control 466.7561
42 10 fused.mu.control 467.5002
43 11 fused.mu.control 434.0221
44 12 fused.mu.control 480.2990
b
participant condition x
45 1 fused.multi 373.0648
46 2 fused.multi 517.5159
47 3 fused.multi 390.2658
48 4 fused.multi 497.2303
49 5 fused.multi 519.7867
50 6 fused.multi 499.7950
51 8 fused.multi 345.8077
52 9 fused.multi 479.1607
53 10 fused.multi 539.5856
54 11 fused.multi 446.9569
55 12 fused.multi 569.5171
--
View this message in context: http://r.789695.n4.nabble.com/Wilcoxon-V-0-tp4637675.html
Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.