Hi > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Filipe Correia > Sent: Wednesday, October 02, 2013 10:32 PM > To: Charles Determan Jr > Cc: r-help@r-project.org > Subject: Re: [R] Interpreting the result of a Wilcoxon (Mann-Whitney U) > test > > Hi, > > Thank you for your answer Charles. > > On Wed, Oct 2, 2013 at 6:50 PM, Charles Determan Jr <deter...@umn.edu> > wrote: > > When you chose a different alternative argument you are asking a > > different null hypothesis. > > I was considering the null hypothesis was expressed through the "mu" > argument. I think I got this idea from R's docs where it states that > "the null hypothesis is that the distributions of x and y differ by a > location shift of mu" (when "a" and "b" are both given and "paired" is > FALSE). Does the "alternative" argument also influence the null > hypothesis in some way that I may be missing? > > My understanding was that by using the "alternative" argument one would > be expressing the alternative hypothesis only. > > > You are looking at a two-tailed, lesser than, and greater than > > hypotheses. Which one you chose is dependent upon your initial > > question. Are you asking generically if your two populations (a and > > b) are different? Are you asking if a > b or a < b? > > Well, I guess I'm asking all of the three... :) Not with the intent to > choose which one fits, but because I was experimenting and making sure > I really understand how I could use R's implementation of the Wilcoxon > test. But I'm intrigued that the answer to "are a and b different" is > not consistent with "is a less than b"... Maybe my understanding of the
Your understanding of statistical test is not correct. When asking /a is not equal b/ you are "splitting" probability of alternative hypothesis to both sides, with asking /a is lower than b/ probability of alternative hypothesis is only at one side of distribution. It is really not a question of R but a question of basic statistics. If some program gave you same answer to those questions you shall get rid of it immediately. Regards Petr > function's arguments and return values is not correct? :\ > > > Thanks, > Filipe > > ______________________________________________ > 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. ______________________________________________ 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.