Re: st: svyset problem 2: using svy with partially complete surveys

["Michael I. Lichter" <mlichter@buffalo.edu>]

Peter,

Your question is whether we can or should, in theory, correct variance 
estimates for the size of the sample relative to the population within 
each poststratum, just as is done for "real" strata. It's not a question 
that ever occurred to me before, but it does make sense.  I don't see 
why this could not be done, although it may be mooted by the 
poststratification adjustments to variance calculation that Stata does. 
Perhaps somebody more knowledgeable than me can answer you properly.

Also, you said:
> An alternative I've considered is to define strata that identify
> unique combinations of lep and gender and then feeding this
> information to the poststratification options in svyset.  Problem here
> is that each PSU, school, now overlaps two strata--one for each gender
> in that school--and it's not clear what the FPC numbers should be for
> each strata.  Am guessing this arrangement will probably violate
> assumptions behind svy.
If you were going to create a poststratum-specific FPC, it would be at 
the student level, not the school level. The original FPC is at the 
school level because that's how you sampled. In creating poststrata 
defined by student characteristics, you are in effect pretending that 
you sampled students, not schools. Your stratum-specific FPC would be at 
the student level, so cross-classification of schools is not a problem.

As for your missing data problem, either using complete cases only or 
following Nick's suggestion about imputation are both probably better 
solutions to your problem than performing some analyses on some cases 
and other analyses on other cases.

Michael
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