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Re: st: friedman test


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: friedman test
Date   Tue, 29 Nov 2011 17:09:51 +0000

A separate comment, obvious enough but I'll make it anyway, is that
most of these values in the example dataset are 0.005, which throws
doubt on the entire analysis, if only in terms of underlining that
adjustment for ties is likely to be needed.


On Tue, Nov 29, 2011 at 4:34 PM, Anders Alexandersson
<andersalex@gmail.com> wrote:
> I agree with Nick. Also, the UCLA webpage
> http://www.ats.ucla.edu/stat/mult_pkg/whatstat/choosestat.html
> has links to comparable SPSS and Stata (and SAS) code. See -findit
> skilmack- if you want the Friedman test when data are missing.
>
> Anders Alexandersson
> andersalex@gmail.com
>
> On Tue, Nov 29, 2011 at 11:16 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>> This presumably refers to Richard Goldstein's -friedman- (SJ 5-1),
>> which is user-written,
>>
>> The help for -friedman- explains
>>
>> " -friedman- expects the raters to be the variables.  This is because -egen,
>>    rank()- ranks observations, not variables.  This expectation differs from
>>    that in some other software."
>>
>> I suspect that you are not comparing like with like.
>>
>> Nick
>>
>> On Tue, Nov 29, 2011 at 3:51 PM, Daniela Ferrante (Lab. Statistica)
>> <daniela.ferrante@med.unipmn.it> wrote:
>>>
>>> I have a question about friedman test. I tried to perform the friedman test
>>> with Stata, R software and SPSS but I get quite different p values with an
>>> equal p value with R and SPSS but different from Stata results. I am wondering
>>> why I get quite different results.
>>> I attach the data:
>>>
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     4,47
>>> 0,005     0,005     12,56
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,1         0,2      1,46
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>> 0,005     0,005     0,005
>>>
>>> Using this data I obtain p=0,69 using Stata software but p=0,06 using R and
>>> SPSS software

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