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st: Testing two cell proportions using tab

From   "Waldo, Daniel R. (CMS/ORDI)" <>
Subject   st: Testing two cell proportions using tab
Date   Fri, 25 Apr 2008 10:53:52 -0400

I am perplexed by the results of some tabulations I ran in Stata10.
Specifically, I am testing for the equality of two cells ... almost
identical to the situation described at

The commands
svy: tab x1 x2 , row
svy: tab x1 x2 , row se

produce different variance-covariance matrices in e(V). The overall
Pearson results appear identical.

So, when I issue the command
test _b[p11]=_b[p71]

the first command produces results that I believe to be simply wrong -
visual inspection of the two cell values being tested overwhelming
suggests no statistically significant difference yet the F value
produced is huge. The second command produces a very small F value.

Having thought that the se option was merely for display purposes, I
would appreciate any thoughts on these results, or on better ways to
accomplish my task.


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