From: Atte Tenkanen <attenka_at_utu.fi>

Date: Thu, 24 Jun 2010 05:16:19 +0300

R-help_at_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. Received on Thu 24 Jun 2010 - 07:33:14 GMT

Date: Thu, 24 Jun 2010 05:16:19 +0300

PS.

Mayby I can somehow try to transform data and check it, for example, using the skewness-function of timeDate-package?

*> 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."
**>
*

> > On Wed, Jun 23, 2010 at 10:27 PM, Atte Tenkanen <attenka@utu.fi> wrote:

*> > > Hi all,
**> > >
**> > > I have a distribution, and take a sample of it. Then I compare
**> that
**> > sample with the mean of the population like here in "Wilcoxon signed
**>
**> > rank test with continuity correction":
**> > >
**> > >> wilcox.test(Sample,mu=mean(All), alt="two.sided")
**> > >
**> > > Wilcoxon signed rank test with continuity correction
**> > >
**> > > data: AlphaNoteOnsetDists
**> > > V = 63855, p-value = 0.0002093
**> > > alternative hypothesis: true location is not equal to 0.4115136
**> > >
**> > >> wilcox.test(Sample,mu=mean(All), alt = "greater")
**> > >
**> > > Wilcoxon signed rank test with continuity correction
**> > >
**> > > data: AlphaNoteOnsetDists
**> > > V = 63855, p-value = 0.0001047
**> > > alternative hypothesis: true location is greater than 0.4115136
**> > >
**> > > What assumptions are needed for the population?
**> >
**> > wikipedia says:
**> > "The Wilcoxon signed-rank test is a _non-parametric_ statistical
**> > hypothesis test for... "
**> > it also talks about the assumptions.
**> >
**> > > What can we say according these results?
**> > > p-value for the "less" is 0.999.
**> >
**> > That the p-value for less and greater seem to sum up to one, and that
**> > the p-value of greater is half of that for two-sided. You shouldn't
**> > ask what we can say. You should ask yourself "What was the question
**> > and is this test giving me an answer on that question?"
**> >
**> > Cheers
**> > Joris
**> >
**> > --
**> > Joris Meys
**> > Statistical consultant
**> >
**> > Ghent University
**> > Faculty of Bioscience Engineering
**> > Department of Applied mathematics, biometrics and process control
**> >
**> > tel : +32 9 264 59 87
**> > Joris.Meys_at_Ugent.be
**> > -------------------------------
**> > Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
*

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