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Re: st: semi-random sampling (how to impose properties of one population onto a subsample of a different population)


From   Austin Nichols <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: semi-random sampling (how to impose properties of one population onto a subsample of a different population)
Date   Sun, 7 Aug 2011 21:35:54 -0400

Ekaterina Hertog--
Do you need a sample?
You could just reweight using a propensity score.
I.e. is this for analysis or for surveying the sampled obs?

On Sun, Aug 7, 2011 at 10:32 AM, Steven Samuels <sjsamuels@gmail.com> wrote:
>
>
> Sorry, I misunderstood. Here's code that you can adapt. Note that you set the sample size you want in the first line
>
> *************CODE BEGINS*************
> **************CODE ENDS**************
>
> On Aug 7, 2011, at 5:05 AM, Ekaterina Hertog wrote:
>
> Dear Steven,
> thank you for your help, however it does not fully solve my problem. Your proposed solution will allow me to roughly preserve the population percentages from the whole sample into a subsample. What I need however, is to impose populations percentages found in a different dataset on a subsample I am creating. Essentially i have two datasets: one of high income women and one of middle income women. High income women tend to be older and are more likely to live in the capital. I need to create a subsample of a dataset of middle income woemn which would match the high income women dataset on age and location characteristics.
> Does anyone know how to do this in Stata 11?
> Ekaterina
>
> On 07/08/2011 09:08, Steven Samuels wrote:
>> 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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