Dear all,
Am I correct in thinking that when we form a model containing interactions,
the main effects making up these interactions should be included in the
model regardless of their significance? i.e. if the term x1^2 significant
and in the model then x1 should also be present even if x1 is non
significant and if x1*x2 is significant and in the model, then x1 and x2
should both be present even if one or both of them is non significant.
Many thanks for your help on this,
All the Best,
Kim.
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