I'm aware of how to plot an interaction from linear regression, but I'm
having some trouble figuring out how to plot an interaction from a Tobit
regression where the predicted values are constrained to fall within the
range of the observed outcome.
For example, my variables are:
alc=alcohol use
race=race (0=white, 1=minority)
pa=postive affect (scale scores range from 1 - 4)
int=race*pa
My Tobit results are:
alc = 1.37 + .42(pa) - 5.89(race) + 1.84(int)
One can rewrite this equation to get the separate equations for white and
minority:
white: alc = 1.37 + .42(pa)
minority: alc = -4.52 + 2.26(pa)
Now consider the equation for minorities, if I compute the predicted value
for alc at the lowest level of pa, I get
minority: alc = -4.52 + 2.26(1) = -2.26
Of course, the lower limit of the observed variable is zero unlike the
latent outcome.
Is there a way to plot this interaction where the predicted alcohol values
fall within the range of the observed outcome?
Thanks in advance for any help.
Mike Frone
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