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x_s
2011 May 06
2
Confidence intervals and polynomial fits
...glm() (a binary logistic regression fit, but I don't think that's important) for a formula that contains powers of the explanatory variable up to fourth. So the fit looks something like this (typing into mail; the actual fit code is complicated because it involves step-down and so forth):
x_sq <- x * x
x_cb <- x * x * x
x_qt <- x * x * x * x
model <- glm(outcome ~ x + x_sq + x_cb + x_qt, binomial)
This works great, and I get a nice fit. My question regards the confidence intervals on that fit. I am calling:
cis <- confint.default(model, level=0.95)
to get the confid...