Suppose I have a mixed-effects model where yij is the jth sample for
the ith subject:
yij= beta0 + beta1(age) + beta2(age^2) + beta3(age^3) + beta4(IQ) +
beta5(IQ^2) + beta6(age*IQ) + beta7(age^2*IQ) + beta8(age^3 *IQ)
+random intercepti + eij
In R how can I get an F test against the null hypothesis of
beta6=beta7=beta8=0? In SAS I can run something like contrast age*IQ
1, age^2*IQ 1, age^3 *IQ 1, but is there anything similar in R?
Thanks in advance,
Gang
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