http://spssx-discussion.165.s1.nabble.com/testing-statistical-dfference-between-medians-of-a-sample-and-a-subsample-extracted-from-the-sample-tp5714777p5714802.html
> Thanks Marta. Another good article on the same topic is Don Zimmerman's
> down a PDF. I managed to get one from a colleague at another university,
). That narrowed the search
>
> Cheers,
> Bruce
>
>
>
> Marta García-Granero-2 wrote
>> Hi:
>>
>> 1) Bruce, see also Anna Hart. "Mann-Whitnet test is not just a test of
>> medians: differences in spread can be important" (BMJ 2001;323:391-3). I
>> lost track of a reference that stated the same for Kruskal-Wallis test,
>> I'll try to dig it (to many files in my external hard disk).
>>
>> 2) Maybe vinikalra could compute a 95%CI for the median of the
>> subsample, and check if the full sample median is included within the
>> limits.
>>
>> Best regards,
>> Marta GG
>>
>> El 21/08/2012 23:32, Bruce Weaver escribió:
>>> I too was wondering why you wanted a test comparing medians. People
>>> sometimes assume that the Wilcoxon-Mann-Whitney test (aka Mann-Whitney U)
>>> compares medians (as opposed to means). But that is only true if the two
>>> populations being compared are identical apart from a shift in location.
>>> And in that case, the test could be said to be comparing means, medians,
>>> or
>>> any other percentile point you might choose.
>>>
>>> By the way, the WMW is quite sensitive to small differences in variance
>>> or
>>> skewness in the populations, which can cause it to reject H0 far too
>>> often
>>> when it is used purely as a test of differences in location. See for
>>> example the nice article by Fagerland & Sandvik (2009).
>>>
>>>
http://www.ncbi.nlm.nih.gov/pubmed/19247980>>>
>>> HTH.
>>>
>>>
>>> Rich Ulrich-2 wrote
>>>> "Parametric" and "median" don't usually go together. See (3)
>>>> for a possible meaning. There are other problems.
>>>>
>>>> First - There is no such thing as a "proper" test for a sub-sample
>>>> versus the whole sample that it comes from. The necessary logic
>>>> says that you compare a sub-sample to the *rest* of the sample.
>>>>
>>>> You may occasionally see a good presentation that does use the
>>>> approximate tests of this sort, for convenience and ease, plus a
>>>> strong desire to accommodate Ns that are unequal. For sub-samples
>>>> with equal Ns, you can use a simple Confidence Interval around the
>>>> overall mean.
>>>>
>>>> Second - Almost nobody actually, ever compares "medians". That
>>>> description is less often accurate than it is an erroneous reference
>>>> to a test of ranks.
>>>>
>>>> Third - The most "non-parametric" way to put a Confidence Interval
>>>> around the median of a single sample (full sample, here?) is to
>>>> end up using ranks of scores in the sample to delimit the range.
>>>> For instance, for a sample of a certain N, the 40th and 60th centiles
>>>> might determine the scores to mark the 95% CI. There is no strong
>>>> reason to expect that CI to be symmetrical around the median. If
>>>> you wanted a "parametric" version of that, I suppose you would use
>>>> the SD to determine a range. Do you want to pick out the samples
>>>> whose medians do not fall in that range?
>>>>
>>>> --
>>>> Rich Ulrich
>>>>
>>>>> Date: Tue, 21 Aug 2012 01:48:46 -0700
>>>>> From: vinikalra@
>>>>> Subject: testing statistical dfference between medians of a sample and
>>>>> a
>>>>> subsample extracted from the sample
>>>>> To: SPSSX-L@.UGA
>>>>>
>>>>> HI all !
>>>>>
>>>>> In a data analysis I am required to perform a statistical test
>>>>> (parametric)
>>>>> to know the statistical difference(if significant) between median of 2
>>>>> sample where one is full sample and another is sub sample extracted
>>>>> from
>>>>> the
>>>>> full sample based on a given characteristics (e.g. respondents
>>>>> belonging
>>>>> to
>>>>> certain age group).
>>>>>
>>>>> Can anyone suggest how togo about it in spss ?
>>>>>
>>>>> regards
>>>> ...
>>>>
>>>
>>>
>>> -----
>>> --
>>> Bruce Weaver
>>> bweaver@
>>>
http://sites.google.com/a/lakeheadu.ca/bweaver/>>>
>>> "When all else fails, RTFM."
>>>
>>> NOTE: My Hotmail account is not monitored regularly.
>>> To send me an e-mail, please use the address shown above.
>>>
>>> --
>>> View this message in context:
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>
>
>
> -----
> --
> Bruce Weaver
>
[hidden email]
>
http://sites.google.com/a/lakeheadu.ca/bweaver/>
> "When all else fails, RTFM."
>
> NOTE: My Hotmail account is not monitored regularly.
> To send me an e-mail, please use the address shown above.
>
> --
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