On Aug 3, 2012, at 11:33 , greatest.possible.newbie wrote: > Thank you for your answer. > The p.adj argument in the kruskal()-function doesn't seem to change > anything... Not even the "bonferroni"-method although it is described as the > most conservative one (multiplying all p-values with the number of > comparisons). I suppose the kruskal()-function is not working properly...
Apparently, the grouping logic doesn't care about p.adj. Not the most fortunate design in my opinion, but try looking at the output with group=FALSE. > On the other hand I doubt the method behind the kruskalmc()-function as this > function doesn't even turn out to detect significant differences between the > grouping variable (which is obviously a severe error). That's not obvious! Did you check all group comparisons? How big are the groups? > Do you think it is justifiable to use the kruskal()-function without > p-adjustment, i.e. doing only pairwise tests like you can do with the > kruskal.test()-function although I obviously want to do multiple > comparisons? > > kruskal(x[,1],x[,2],p.adj="bonferroni") > #Yields exactely the same results. > #Groups, Treatments and mean of the ranks > #a 11 304.4 > #ab 9 296 > #ab 7 286.6 > #ab 8 278.2 > #ab 10 268.7 > #ab 2 250.6 > #ab 6 242.9 > #ab 1 242.1 > #ab 3 239.4 > #ab 5 228.8 > #b 4 219.5 > > > kruskalmc(x[,2],x[,2]) > > #Multiple comparison test after Kruskal-Wallis > #p.value: 0.05 > #Comparisons > # obs.dif critical.dif difference > #[......] > #6-9 54.0 162.02688 FALSE > #6-10 69.5 159.04584 FALSE > #6-11 94.5 133.02196 FALSE > #7-8 18.0 160.00778 FALSE > #7-9 35.0 169.78370 FALSE > #7-10 50.5 166.94123 FALSE > #7-11 75.5 142.36796 FALSE > #8-9 17.0 165.54197 FALSE > #8-10 32.5 162.62538 FALSE > #8-11 57.5 137.28174 FALSE > #9-10 15.5 172.25281 FALSE > #9-11 40.5 148.56074 FALSE > #10-11 25.0 145.30369 FALSE > -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.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.
