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Re: st: offset() option in glm models
At 10:28 AM 5/14/2009, Weichle, Thomas wrote:
Dear Statalisters,
Can someone please explain the use of the offset() option in glm models?
I've searched the help menu documentation and the explanation doesn't
seem clear to me. Thanks.
It includes the specified variable in the model with coefficient
constrained to 1, which, I guess, is useful if you think a
coefficient should be one. For example, maybe the var is a lagged
version of the dependent variable, so in effect you are running a
regression on a change score. Or, the offset option can be an
alternative to the exposure option, e.g. instead of exposure(timevar)
you could have offset(lntimevar). I think it is mostly a convenience
as there are often other ways of achieving the same goal, e.g. you
can use the constraints option.
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Richard Williams, Notre Dame Dept of Sociology
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