[R] Calculating critical values

[Adam D. I. Kramer]

Hello,

 	I have an HLM-like situation: a data frame with rows representing
individuals, and columns representing some statistics for the individual
(e.g., a mean and variance for that individual, plus the number of
observations for that person).

 	I'm interested in computing a confidence interval around each
individual's mean, but to do that, I would need to know the critical t-value
for each individual.

 	Ergo, is there any sort of function that returns a critical t-value
for a given p/alpha and df?

Thanks,
Adam Kramer