Dear All
Eve raises a fair query, several authors using different ways to
describe the various types of term in a model.
'Two-way interaction' is a safe way, people tend to know what you
mean by that. 'First order' is not so safe, the model will show
curvature with a two-way interaction present within it and some
people would argue that this is second order. And how do you
distinguish between AB and ABC if they are both 'first order'?
Two-way first order might seem OK, with ABC then being three-way
first order, until you come across A(Bsq). Now is that a two-way
first and second order, or a mixed first and second order two way, or
three way second and first.........? continued page 94.
The expression 'order' is used differently depending on context.
I suggest you stick with 'two-way interaction'.
regards
Dave Stewardson
ISRU {Industrial Statistics Research Unit}
MMME {Department of Mechanical, Materials and Manufacturing Engineering}
Stephenson Building
University of Newcastle upon Tyne
Tyne & Wear
England
GB - NE1 7RU
TEL 00 44 191 222 6244
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