Simple statistics question, but can't figured out.
What is the critical value t* for constructing a 99%, percent confidence interval for a mean with 11 degrees of freedom?
My answer for this is 3.169 where df = 10 and two tails' value is 0.01
But the correct answer is 3.106 where df = 11.
I am confused why we don't minus 1 here for df.
Don't we df = n -1 where n is the sample size?