Re: [R] Significance test for discrete data

From: Peter Dalgaard <P.Dalgaard_at_biostat.ku.dk>
Date: Thu, 10 May 2007 14:37:16 +0200

Christophe Pallier wrote:
> The Wilcoxon paired rank sign test assumes symmetry.
> (cf. http://www.basic.northwestern.edu/statguidefiles/srank_paired_alts.html
> )
>
>
...of differences, and under the null hypothesis. This is usually rather uncontroversial. With only 7 different outcomes for differences (-3:3) you need to pay attention to ties, though. R's wilcox.test will get the asymptotic variance right, but cannot do exact test in that case, so you may want to check out package ExactRankTests.

> Christophe Pallier
>
> On 5/10/07, Alexander Kollmann <kollmann@telbiomed.at> wrote:
>
>> Hello,
>>
>> given situation:
>>
>> - pre / post test comparison of discrete, paired data [values can be
>> 1,2,3,4].
>> - the data are neither normal distributed nor symetric
>>
>> Which test should I use to calculate the p-value? Is the wilcoxon rank sum
>> test ok ?
>>
>>
>> Alex
>>
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>
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-- 
   O__  ---- Peter Dalgaard             Ă˜ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
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Received on Thu 10 May 2007 - 12:43:59 GMT

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