Hi
On 22 Apr 2001, Donald Burrill wrote:
> If I were doing it, I'd begin with a "full model" (or "augmented model",
> in Judd & McClelland's terms) containing three predictors:
> y = b0 + b1*X + b2*A + b3*(AX) + error
> where A had been recoded to (0,1) and (AX) = A*X. [1]
A number of sources (e.g., Aiken & West's Multiple regression:
testing and interpreting interactions) would recommend centering
X first (i.e., subtracting out its mean to produce deviation
scores). You might also consider whether dummy coding (0,1), as
recommended by Donald, would be best or perhaps effect coding
(-1, 1).
Best wishes
Jim
============================================================================
James M. Clark (204) 786-9757
Department of Psychology (204) 774-4134 Fax
University of Winnipeg 4L05D
Winnipeg, Manitoba R3B 2E9 [EMAIL PROTECTED]
CANADA http://www.uwinnipeg.ca/~clark
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