Hi All,
I am trying to fit a linear regression between the tool speed and the tool
type ( type A, Type B , Type C) where the response is the tool speed and the
regressor is the tool type.
I introduced two dummy variables X1 and X2 as follows
X1 X2
Tool A 0 0
Tool B 0 1
Tool C 1 0
Model<-Lm (y~X1+X2)
My question is on the residual plot, it looks like three cluster because I
have three tool types. Is such a plot is ok with the constant variance
assumption and normality (below is a link for the plot)?I have never seen
such a plot of the residuals
http://www.nabble.com/file/p22972254/question.JPG question.JPG
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