Re: st: Sample with weights

[Nick Winter <nw53@cornell.edu>]

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
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