Is there anything for me? There is a lot of data, n=2418, but there are also a lot of ties. My sample n≈250-300
i would like to test, whether the mean of the sample differ significantly from the population mean. The histogram of the population looks like in attached histogram, what test should I use? No choices? This distribution comes from a musical piece and the values are 'tonal distances'. http://users.utu.fi/attenka/Hist.png Atte > On 06/24/2010 12:40 PM, David Winsemius wrote: > > > > On Jun 23, 2010, at 9:58 PM, Atte Tenkanen wrote: > > > >> Thanks. What I have had to ask is that > >> > >> how do you test that the data is symmetric enough? > >> If it is not, is it ok to use some data transformation? > >> > >> when it is said: > >> > >> "The Wilcoxon signed rank test does not assume that the data are > >> sampled from a Gaussian distribution. However it does assume that the > >> data are distributed symmetrically around the median. If the > >> distribution is asymmetrical, the P value will not tell you much about > >> whether the median is different than the hypothetical value." > > > > You are being misled. Simply finding a statement on a statistics > > software website, even one as reputable as Graphpad (???), does not > mean > > that it is necessarily true. My understanding (confirmed reviewing > > "Nonparametric statistical methods for complete and censored data" > by M. > > M. Desu, Damaraju Raghavarao, is that the Wilcoxon signed-rank test > does > > not require that the underlying distributions be symmetric. The above > > quotation is highly inaccurate. > > > > To add to what David and others have said, look at the kernel that the > > U-statistic associated with the WSR test uses: the indicator (0/1) of > xi > + xj > 0. So WSR tests H0:p=0.5 where p = the probability that the > average of a randomly chosen pair of values is positive. [If there > are > ties this probably needs to be worded as P[xi + xj > 0] = P[xi + xj < > > 0], i neq j. > > Frank > > -- > Frank E Harrell Jr Professor and Chairman School of Medicine > Department of Biostatistics Vanderbilt University ______________________________________________ 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.
