From | "Michael I. Lichter" <MLichter@Buffalo.EDU> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: single sample pre/post comparison of proportions |
Date | Wed, 10 Jun 2009 22:41:04 -0400 |
Is a two-sample test of proportions as in -prtest- reasonable under these circumstances, given a reasonable N? (The actual N=270, which should be OK for -prtest-'s asymptotic statistics, I think.) I think McNemar's test and Cochran's test are inappropriate (like the chi-square test) because they are ultimately tabular and there cell where pre=YES and post=NO is empty.
The specifics are that a group of physicians was presented with an educational intervention intended to prompt adoption of a set of behaviors. Some physicians had already adopted those behaviors, so their pre status (ADOPT = YES) did not change after the intervention; only physicians who had not adopted at the pre-test could change adoption status after the intervention.
There must be some fairly standard way of handling this in epidemiology where for some conditions people can go from disease-free to diseased, but not from diseased to disease-free.
Thanks for any suggestions. Michael * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/
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