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Re: st: Using ksmirnov


From   Morrison Hodges <hodge002@umn.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Using ksmirnov
Date   Wed, 5 Sep 2012 11:09:51 -0500

Nick and Maarten, thank you. My second example does work, when I pick a variable that has data (I haven't any patients in Group 3 yet). Testing Groups 1 and 2 worked as advertised. My bad, as usual. I've downloaded -stripplot- and will look it over.
Morry

On Sep 5, 2012, at 10:14 AM, Maarten Buis <maartenlbuis@gmail.com> wrote:

> On Wed, Sep 5, 2012 at 4:41 PM, Morrison Hodges wrote:
>> I'm trying to use ksmirnov to compare 2 distributions to determine if there are any differences in the distribution of the variables.
>> 
>> I have a .dta file with 179 patients. Each patient is classified as being in one of 7 groups from 1 to 7, i.e., group==1, group==2, etc. I want to compare the same variable between 2 groups. All variables are already sorted, from lowest to highest.
> 
> For such a small sample size like that I would use Nick Cox's
> -stripplot- (see: -ssc desc stripplot-). The power of tests like
> -ksmirnov- is usually pretty bad, so in small sample sizes you are not
> going to find anything that is not glaringly obvious if you just
> looked at the data. On the other hand you will in all likelihood miss
> lots of real an interesting patterns if you focus on such low power
> tests. So, there is no added value to be got from these tests and a
> real chance of a loss.
> 
> -- Maarten
> 
> ---------------------------------
> Maarten L. Buis
> WZB
> Reichpietschufer 50
> 10785 Berlin
> Germany
> 
> http://www.maartenbuis.nl
> ---------------------------------
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