[R] Wilcoxon signed rank test and its requirements
Frank E Harrell Jr
f.harrell at Vanderbilt.Edu
Fri Jun 25 14:59:37 CEST 2010
The central limit theorem doesn't help. It just addresses type I error,
On 06/25/2010 04:29 AM, Joris Meys wrote:
> As a remark on your histogram : use less breaks! This histogram tells
> you nothing. An interesting function is ?density , eg :
> See also this ppt, a very nice and short introduction to graphics in R :
> 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?
Frank E Harrell Jr Professor and Chairman School of Medicine
Department of Biostatistics Vanderbilt University
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