Residuals versus fits plot (from Minitab)

Question

I performed a multiple linear regression and after checking my results everything seems to be great, but when I checked the residuals I noticed this patterns in the attached figure and I am not sure if it's right or not. I think there are two (or maybe three) groups. Am I right? Or this is a a random distribution? If there are two or more groups, what should I do next?

Thanks!

well, If I were you I would check distribution of residuals since in MLR the residuals are supposed to be normally distributed. It should be available in Minitab as far as I remember. — gunakkoc, Oct 13 '17 at 00:12

score 1 · Answer 1 · answered Oct 13 '17 at 01:35

1

You seem to have 3 groups of predicted values. This looks like you have one categorical predictor that takes 3 levels and one or more continuous predictor, but that the categorical predictor has a stronger relationship. That is not, in itself, a problem. But if the residuals are related to the fitted values, that is a problem. However, you have so little data that it is hard to tell.

The fact that you have so little data makes me worry about overfitting.

answered Oct 13 '17 at 01:35

Peter Flom

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How can I check of the residuals are related to the fitted values? – Billo Oct 13 '17 at 03:18
Ordinarily, you would look at a plot like this one. It's just that with so few subjects, it's hard to see any pattern. – Peter Flom Oct 13 '17 at 11:19
The usual way to express thanks here is to upvote. And, if your question is now answered, you can accept my answer. – Peter Flom Oct 15 '17 at 21:11

Residuals versus fits plot (from Minitab)

1 Answers1