How to test for intercept differences when slopes are different? has any sense to do it?

12 December 2017 1 785 Report

Dear RGaters,

I ran the following regression

Final weight~treatment+Initial weight+treatment:Initial weight

where treatment is a binary variable (treated vs. untreated animals)

The interaction term is significant so the slopes for each treatment is different. Is there any test in R to check whether there are statistical differences among the intercepts of the two treatments?

Moreover, is there any sense to test for it?

Thanks in advance

Jochen Wilhelm

The intercepts give you the esimated weight for animals with an initial weight of zero in the reference (untreated) group. I don't see that this should be something.

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