# Wilcoxon V = 0

5 messages
Open this post in threaded view
|

## 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
Open this post in threaded view
|

## Re: Wilcoxon V = 0

 This post has NOT been accepted by the mailing list yet. Hello, Your question is whether it is possible to have V=0. Check this link.  (http://www.r-bloggers.com/wilcoxon-signed-rank-test/).  If you calculate V based on the method shown in the link, you will get 0.  diff1<-a\$x-b\$x  diff1<-diff1[diff1!=0] diff1.rank<-rank(abs(diff1)) diff1.rank.sign<-diff1.rank*sign(diff1) ranks.pos<-sum(diff1.rank.sign[diff1.rank.sign>0])  ranks.neg<- -sum(diff1.rank.sign[diff1.rank.sign<0])  ranks.pos [1] 0 > ranks.neg [1] 66 A.K.
Open this post in threaded view
|

## Re: Wilcoxon V = 0

 In reply to this post by Naomikb 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: [hidden email] [mailto:r-help-bounces@r- > project.org] On Behalf Of Naomikb > Sent: Tuesday, July 24, 2012 4:36 PM > To: [hidden email] > 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. > > ______________________________________________ > [hidden email] 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. ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.