[R] Wilcoxon signed rank test and its requirements

[Joris Meys]

As a remark on your histogram : use less breaks! This histogram tells
you nothing. An interesting function is ?density , eg :

x<-rnorm(250)
hist(x,freq=F)
lines(density(x),col="red")

See also this ppt, a very nice and short introduction to graphics in R :
http://csg.sph.umich.edu/docs/R/graphics-1.pdf

2010/6/25 Atte Tenkanen <attenka at utu.fi>:
> 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

You should think about the central limit theorem. Actually, you can
just use a t-test to compare means, as with those sample sizes the
mean is almost certainly normally distributed.
>
> i would like to test, whether the mean of the sample differ significantly from the population mean.
>
According to probability theory, this will be in 5% of the cases if
you repeat your sampling infinitly. But as David asked: why on earth
do you want to test that?

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
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