# Re: st: Sample with weights

 From Nick Winter To statalist@hsphsun2.harvard.edu Subject Re: st: Sample with weights Date Fri, 30 Sep 2005 14:43:36 -0400

```At 02:00 PM 9/30/2005, you wrote:
```
```Willard wrote:
I have a population of company's. I want a sample from this population,
but the probability of a company to be sampled has to be equivalent with
the number of employees (let's call this "size").
```

I would take an approach like this:

(1) Calculate for each company the probability of inclusion. This is (sample size) * (size of company / total of company sizes). So assuming a sample size of 100:

. sum size
. gen prob = 100 * ( size / r(sum) )

(2) Then select the sample based on these probabilities

. gen u = uniform()

. gen insamp = u < prob

The problem is that this approach generates an *average* sample size of 100, but not exactly 100 in every case. Thoughts?

Nick Winter

________________________________________________________
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Assistant Professor 607.255.4530 f
Department of Government nw53@cornell.edu e
Cornell University falcon.arts.cornell.edu/nw53 w
308 White Hall
Ithaca, NY 14853-4601

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