Hi,
With Stata 9, I am using survey regression with the subpop command e.g.,
svy, subpop(var1): reg dep1 ind1
The regression result reports "Number of obs" and "Subpop. no. of obs".
Based on running a few scenarios, the "Number of obs" includes all
observations that have non-missing values for the regression variables,
including the weights. This is as expected; however, the "Subpop. no. of
obs" seems to include all observations that have a "1" for the subpop,
including those observations that have missing values for the regression
variables.
An actual example is below where I would have thought "Subpop. no. of obs"
would have been 5329, not 5436. (This is a simple example. I am estimating
several models with different sets of variables and am only able to find
out how many observations Stata is really using by running an extra
command such as: count if !missing(var1, var2, etc.).)
Lastly, I know if I am using the Taylor series approach to estimate
parameter standard errors within a subpopulation, subpop is required
(i.e., this is wrong: svy: reg dep1 ind1 if female==1). However, if I am
using replicate weights, is subpop required?
Any help would be appreciated.
Thanks,
Brent Fulton
Petris Center at UC Berkeley
www.petris.org
webuse nhanes2jknife, clear
count
replace age=. in 401/600
tab female
tab female if age!=.
svy, subpop(female): reg bpsystol age
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