Abstract
Consider a model y
i
= β0 + β1
x
i1 + β2
x
i2 + e
i
, i = 1,…, n, with two explanatory variables. The synergy phenomenon deals with the case when . It is shown here that in the model with the regression vectors x
1 = (x
11,…, x
n1)′ and x
2 = (x
12,…, x
n2)′ such a phenomenon does not appear for all possible observation vectors y = (y
1,…, y
n
)′, if and only if
or 1.
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