Prior to the steps below, enter the data as appropriate for the analyses (described elsewhere). As always, the following commands should be typed directly in the R console window.
Get the sample size, mean, and standard deviation for the variable.
length(Outcome)
mean(Outcome)
sd(Outcome)
Get the mean and its confidence interval.
t.test(Outcome)$conf.int
Also, you can change the width of the confidence interval if desired.
t.test(Outcome,conf.level=.99)$conf.int