> From: Duncan Murdoch > > On Thu, 19 Aug 2004 13:42:21 -0300 (ADT), Rolf Turner > <[EMAIL PROTECTED]> wrote : > > > > >You wrote: > > > >> What's the difference between t.test(x, y) and > pairwise.t.test()? Is > >> it just that the former takes two vectors, whereas the > latter takes a > >> vector and a factor? > > > > No. The pairwise.t.test() function (according to the help > > file) does a multiplicity of t-tests, on more than two > > samples, adjusting the p-value to compensate for the > > multiplicity by various methods. > > > > IMHO the name of this function is bad, because to me it > > suggests doing ***paired*** t-tests, which would trip up the > > naive user, who probably wouldn't notice or would ignore the > > "t tests with pooled SD" message in the output. As one of > > the Ripley fortunes says ``It really is hard to anticipate > > just how silly users can be.'' But why go out of the way to > > give them a chance to be silly? > > And Jack wrote: > > >But the documentation, which I valiantly tried to make sense > of BEFORE > >asking my stupid question, is not clear enough for this > particular idiot. > >Might I suggest that the documentation be altered? It could > use an example > >(as in, real-life applied statistical problem) of when > pairwise.t.test() > >ought to be used, and why t.test(paired=TRUE) would be > inappropriate in that > >context; it could also use a reference to some published > paper, website or > >some such that explains the rationale and correct procedure > for using this > >test. > > I think it's unlikely that we would rename the function; it's been > around a while with its current name so that's a bad idea. On the > other hand, clearer documentation is always a plus: why not submit > some?
I guess this is sort of related to the thread on whether R is good for non-statisticians... The help pages in R are sort of like *nix man pages. They give the technical information about the topic, but not necessarily the background. E.g., the man page for `chmod' does not explain file permissions in detail: the user is expected to learn that elsewhere. Perhaps other stat packages do it differently? Does SPSS manuals detail what its t-test procedure does, including which t-test(s) it does and when it's appropriate? That might make it easier on users, but I still think the users should learn the appropriate use of statistical procedures elsewhere... Best, Andy > Duncan Murdoch > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > > ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
