Find the value of E the margin of error for c099 n15 and s

Find the value of E, the margin of error, for c=0.99, n=15 and s = 5.4

Please explain step by step how to get using a graphic calculator.

Solution

The degree of freedom =n-1=15-1=14

Given a=0.99, t(0.005, df=14) =2.977

So the margin of error is t*s/vn = 2.977*5.4/sqrt(15)

=4.15