Message-ID: <Pine.LNX.4.64.0809221616350.32341@homer21.u.washington.edu>
Date: 2008-09-22T23:18:51Z
From: Thomas Lumley
Subject: Weights for polr
In-Reply-To: <alpine.LRH.1.10.0809221851480.30340@yoknapatawpha.pols.columbia.edu>
On Mon, 22 Sep 2008, Gregory Wawro wrote:
> Hello,
>
> I'm estimating an ordered logit model on a probability weighted survey
> sample.
You could use svyolr() in the survey package.
> polr permits case weights with the "weights" option, but I cannot
> figure out from existing documentation what it actually does with these
> weights.
They are frequency weights.
> I'm concerned about this because I get somewhat different results
> using Stata's ologit command with the pweights option
You should get the same point estimates, but different standard errors.
> and very different
> results using proc logistic in SAS with its weight option.
Again, it should be the same point estimates but different standard
errors.
> So my basic
> question is whether or not it is appropriate to use the weight option for
> polr with my data.
No.
-thomas
Thomas Lumley Assoc. Professor, Biostatistics
tlumley at u.washington.edu University of Washington, Seattle