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RE: st: Statistical advice about multiple comparison...

From   jverkuilen <>
To   <>
Subject   RE: st: Statistical advice about multiple comparison...
Date   Fri, 25 Jul 2008 18:52:21 -0400

Nonparametric tests tend to lose a lot of power when you have many ties as you will have here. 

You may benefit from a model for discete ordinal data such as -ologit-. However it is not set up for repeated measures analysis. You may find -gllamm- helpful there. See 

-----Original Message-----
From: "Yupa" <>
To: "Statalist" <>
Sent: 7/25/2008 6:04 PM
Subject: st: Statistical advice about multiple comparison...

Dear statalisters,

I have 9 test items and each item is scored ordinally 1 to 4 points 
(distance between points isn't equal).
The test is administered to two populations; in the first population 
each item is taken two times for each subject (at different ages). The 
second population served as reference.
Some of the test items show a ceiling effect (aren't able to 
discriminate at high end of the scale, and lower scores are not 
I have to compare the results of each item between the two timepoints of 
the first population and between each timepoint of the first population 
versus the reference population.
I think that an equality test for matched data is adequate for the first 
comparison (signrank) and an equality test for unmatched data (ranksum) 
for the second. 
Am I right or am I missing something?
May I analyze the data in a different way (different tests)?

Thanks in advance!
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