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Re: st: Centering variables for interactions and using mi regress

From   Richard Williams <[email protected]>
To   [email protected]
Subject   Re: st: Centering variables for interactions and using mi regress
Date   Sun, 16 Jan 2011 23:06:56 -0500

At 09:06 PM 1/16/2011, Amy S wrote:
Richard, Thanks for the advice and passing along Paul's previous advice on the subject! That is interesting - a little counterintuitive, but certainly easier to implement.

Incidentally, here is the earlier discussion on how to impute values when you have interaction terms:

I interpret this as meaning that Allison would NOT approve of using commands like -mi passive-. For example, the Stata help for -mi passive- says
A passive variable is a variable that is a function of imputed variables or of other passive variables. For instance, if variable age were imputed and you created lnage from it, the lnage variable would be passive. The right way to create lnage is to type

. mi passive: generate lnage = ln(age)

Simply typing

. generate lnage = ln(age)

is not sufficient because that would create lnage in the m = 0 data, and age, being imputed, varies across m.

I think Allison would disagree and say that, before imputing, do

. generate lnage = ln(age)

and then include lnage in the list of variables you impute values for. I don't know if everyone agrees with Allison, but if he is right it seems to me you would probably never use -mi passive-.

Richard Williams, Notre Dame Dept of Sociology
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