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Re: st: semi-random sampling


From   Steven Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: semi-random sampling
Date   Sun, 7 Aug 2011 01:08:26 -0400

The following code shows how to take a 10% sample within categories formed by two variables. The sample and whole population percentages will be approximately the same, with the agreement better for larger within-cell sample sizes.

Steve

*************CODE BEGINS*************
sysuse auto, clear
expand 6
set seed 842655
recode rep78 1/2=5 .=5
tab rep78 foreign, cell
sample 10, by(foreign rep78)
tab rep78 foreign, cell
**************CODE ENDS**************



On Aug 6, 2011, at 4:23 PM, Ekaterina Hertog wrote:

Dear all,
I need to take a subsample of observations from a big dataset making sure that the people in the subsample have a given geographic and age profile. I need to make sure that, say, 50% of people in the subsample come from the capital and 50% from other towns. Within each of these 2 locations I want to preserve a certain age structure: say in a city: 3 people ages 23, 4 people aged 24 …
Within those geographic and age profiles I want to select the observations randomly. Is it possible to do that in Stata 11? Any thoughts on how I would go about it?

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