The amount of time it takes a bat to eat a frog was recorded for each bat in a random sample of 12 bats. The resulting sample mean and standard deviation were 21.9 minutes and 7.7 minutes, respectively. Assuming it is reasonable to believe that the population distribution of bat mealtimes of frogs is approximately normal,

a. Construct a 95% confidence interval for the mean time for a bat to eat a frog.

Using R studio => 21.9+c(-1,1)*qt(1.95/2,11)*7.7/sqrt(12)

b. Construct a 95% confidence interval for the variance of the time for a bat to eat a frog.

How do I calculate the confidence interval for the variance using R studio too?