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The second model is:-

Log(crh)= b0 + b1*time + b2*hvinf + b3*(time*hvinf).

I can get similar prediction equations as above. In both these models, the intercept and the coefficient for time are same ie, b0 and b1 is same in both the regression models.

In both the above regression models, I included a quadratic term for time, modifying the models as given below:

Model-1: Log(crh)= b0 + b1*time + b2*time^2 + b3*hvptb + b4*(time*hvptb).

Model-2: Log(crh)= b0 + b1*time + b2*time^2 + b3*hvinf + b4*(time*hvinf).

On estimating the models I find that the values of b0 and b1 are not the same for the two models. Hence the prediction equation for the normal people are different in the two models. Also, this is the simplified version of the problem. I intend to estimate the two models using gllamm.

Id appreciate it if anybody can shed some light on this issue.



Leny Mathew
Data Analyst
Division of Perinatal Research
Department of Obstetrics/Gynecology
Drexel University College of Medicine
245 N. 15th Street, 17th Floor
Mail Stop 495
Philadelphia, PA  19102
Phone:   215-762-2069

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