On Wed, Sep 24, 2008 at 01:37:49PM +0800, John Darrington wrote: > Jason and I were discussing the Mann-Whitney test on IRC last week, > which inspired me to look up the literature on it. > > One interesting paper I found is Bergmann, Ludbrook and Spooren, > "Different Outcomes of the Wilcoxon-Mann-Whitney Test from Different > Statistics Packages", The American Statistician 54(1), 2000, pp 72-77 > > From their conclusion: > "... statistics packages provide very inadequate documentation in > their manuals... As a consequence, the results can be dangerously > misleading. > Investigators cannot rely on the popular, general purpose, > microcomputer statistics programs ... to provide an accurate outcome > of the WMW test." > > Earlier in the paper, they say the following about spss: > > "The second `exact' p value presumably results from Dineen and > Blakeksley (1973) algorithm, even though this is invalid when there > are ties." > > > We ought to think very carefully therefore when implementing this in > PSPP, and I rather agree with the authors that most stats programs' > documentation is non-existent.
Then I think we should pick a "good" algorithm from the literature and implement that. Then mention it in the manual, as well as the reason for the discrepancy with the other software. -Jason _______________________________________________ pspp-dev mailing list [email protected] http://lists.gnu.org/mailman/listinfo/pspp-dev
