http://spssx-discussion.165.s1.nabble.com/testing-statistical-dfference-between-medians-of-a-sample-and-a-subsample-extracted-from-the-sample-tp5714777p5714789.html
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
> 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
>
[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.
>
> --
> View this message in context:
http://spssx-discussion.1045642.n5.nabble.com/testing-statistical-dfference-between-medians-of-a-sample-and-a-subsample-extracted-from-the-sample-tp5714777p5714788.html> Sent from the SPSSX Discussion mailing list archive at Nabble.com.
>
> =====================
> To manage your subscription to SPSSX-L, send a message to
>
[hidden email] (not to SPSSX-L), with no body text except the
> command. To leave the list, send the command
> SIGNOFF SPSSX-L
> For a list of commands to manage subscriptions, send the command
> INFO REFCARD
>
command. To leave the list, send the command