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From | "JVerkuilen (Gmail)" <jvverkuilen@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: Can I change the intercept in a linear regression model |
Date | Sat, 20 Apr 2013 10:11:46 -0500 |
On Sat, Apr 20, 2013 at 6:57 AM, Daniel Herbert Opi <opi.herbert@gmail.com> wrote: > > I would like to run this model with the intercept instead of running > through zero it runs through a specified value i.e the mean of my > continuous variable. > > Is there a way of doing this in Stata? Stata itself has nothing to do with it per se. The intercept is the predicted value of the dependent variable when all X variables are 0. So if you move the 0 for the X variables you move the intercept (but not the slopes). Thus if you subtract out whatever value you want from the relevant X variable you make the intercept interpretable, assuming that 0 for the X variable is not itself interpretable. I often recommend in class that all continuous predictors be centered, either on the sample mean or some other relevant number, such as a population mean or scale norm if one is available. Example: If you were using an IQ test score as a predictor, it is typically the case that IQ tests have a mean of 100 and standard deviation of 15 by convention. Thus is might make sense to subtract 100 from all scores, not the sample mean. There are sometimes reasons not to, but it's usually pretty good practice. Basically just make the new variables you want using generate and egen. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/