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RE: st: AW: Problem with logit


From   Lee Sieswerda <Lee.Sieswerda@tbdhu.com>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: AW: Problem with logit
Date   Thu, 7 Aug 2003 17:22:00 -0400

Herve wrote in response to roger webb:

***** 
le 7/08/03 12:03, roger webb à roger.webb@man.ac.uk a écrit :

>With this type of result its best to tabulate the data and look at the 
>individual cell values. Zero cell values will be the cause of the 
>'successes and failures completely determined' message. Logistic 
>regression isn't a valid method for your data set. Even without the 
>zero cell values, your data are still far too sparse, especially for 
>creating multivariate models. I suggest you forget it and run simple 
>crosstabs using Fisher exact tests for significance testing.

I can't tabulate the values because PA and NA are "continuous" variables
(unit-weighted sums of items).
*******

Herve:
You can tabulate the values of PA and NA. You just have to categorize them
first. Given your low sample size, dichotomizing may be your best option.
Sounds to me like this could be turned into a set of 2x2 tables and analyzed
using Mantel-Haenszel methods.

Lee Sieswerda, Epidemiologist
Thunder Bay District Health Unit
Lee.Sieswerda@tbdhu.com






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