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Re: st: Treating ind. vars in logit


From   Richard Williams <richardwilliams.ndu@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Treating ind. vars in logit
Date   Sat, 20 Apr 2013 10:11:11 -0400

I would code it as 1 to 5. It wouldn't be unusual just to treat it as continuous. If you want to do a formal test of whether or not that is legit, do something like

logit y x
est store m1
logit y i.x
est store m2
lrtest m1 m2, force

If the difference is not significant treating as continuous is ok. Even if it is significant you can assess how horrible it is to treat as continuous, e.g. how much do the predicted values differ under the two models?

Sent from my iPad

On Apr 20, 2013, at 9:44 AM, Athinagoras Konstantinidis <athikons@gmail.com> wrote:

> Hello,
> 
> My DV is a binary variable (Yes/No) and I am using a logit regression analysis.
> 
> As for my independent variables,there are three I'm primarily
> interested in. They are all ordinal categorical variables,each of
> which is of the form:
> 
> Strongly Agree
> Agree
> Indifferent
> Disagree
> Strongly Disagree
> 
> Whats the best way to include those variables in the model?
> 
> I could arbitrarily plug some ordered values to each answer (e.g. -10
> for "Strongly Disagree", -5 for "Disagree", 0 for "Indifferent", etc).
> 
> I could create dummies for each category and put them into the regression.
> 
> Or,finally, I could create one dummy for each variable which divides
> the categories in half and put them into the regression e.g. dummy=1
> if ("Str. agree" or "Agree") and dymmy=0 if ("Indif." or "Disagree" or
> "Str. Disagree")
> 
> Which one of the three would you propose I do or, do you recommend any
> other alternatives?
> 
> Appreciate your time.
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