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Re: st: Sample Wegihts


From   Steve Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Sample Wegihts
Date   Wed, 10 Mar 2010 09:42:05 -0500

Stas's is absolutely correct. Probability weights must be based on the
overall probability of selection.  The same principle is the basis of
network sampling.

A few years ago,  a telephone survey company supplied us two sets of
weights, because they had taken a second survey to bring the sample
size up. I learned that this had been standard practice for years. Not
surprisingly, their staff did not include a statistician.

The second set of weights would have been correct if they had added a
new stratum to the population and done the second survey in that
stratum only.

-Steve

On Wed, Mar 10, 2010 at 12:47 AM, Michael Lichter <mlichter@fastmail.fm> wrote:

Stas said:

>>overall P[ selection ] = P[ to be selected in the first sample ] + P[ to be selected in the second sample ] - P [ to be selected in both ] = 1 - (1-P[first])*(1-P[second])

Is this correct even with if the first sample is an SRS and the second
is clustered? I can't show otherwise, but it doesn't feel right that
every case in a specific urban area should have the same weight
regardless of which sample it was drawn from.


-- 
Steve Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
845-246-0774
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