Dear all, I want to compare the efficiency of 2 methods in extracting proteins from algal samples. I collected 6 independant algal samples and I extracted 3 by the method 1 and 3 others by the method 2. So I have 2 groups of 3 samples, that are not paired. I would like to know if the results obtained by these 2 methods are significantly different, I hope method 2 to be more efficient than method 1. As I have few data I went for the Mann-whitney test:
method1=c(35,40,56) method2=c(90,110,115) wilcox.test(method1,method2,paired=FALSE,alternative="less") Wilcoxon rank sum test data: method1 and method2 W = 0, p-value = 0.05 alternative hypothesis: true location shift is less than 0 As I have a small number of samples, I would prefer to compare the U value of the Mann-Whitney test to critical value for table rather than to rely on the p-value. Is W value correspond to U value ? >From the help I understand that W=U+m*(m+1)/2, is this true ? In the case it is, my U values would be U=W-6=-6!! I thought that a U value could not be neagtive. I would be happy to have any information about how to obtain the U value from the Mann-Withney test (wilcox.test()) in order to be able to compare it with table of critical U value commonly found. Thanks a lot for your time and help Have a nice day, Chloé -- View this message in context: http://r.789695.n4.nabble.com/U-value-from-wilcox-test-tp2332811p2332811.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@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.
