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My question is in relation to my previous query about interaction terms. I have two regression models:
1) ln(y)= constant + b1*(time) + b2*(group)
In this model group is an indicator variable denoting membership in group1 or group2. On fiting this model, the value of b2 was .29 indicating a 34 percent additional increase in y for the people in group2.
The second model that I fitted included the interaction between group and time.
2) ln(y)= constant + b1*(time) + b2*(group) + b3*(group*time)
In this model , the group is not significant but the interaction effect is. But the effect of the interaction reduces to 2.6 percent (b1=.0822, b3=.026).
How does one explain (In plain English) the drastic reduction in the effect of time on y for the group2 people between the two models?
Thank you in advance for any suggestions
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org:Drexel University College of Medicine;OB/GYN control