Question

Thirty randomly selected students took the calculus final. If the sample Jean was 95 and the standard deviation was 6.6, construct a 99% confidence interval for the mean score of all students

Answer 1

Given:

n = 30 students

sample mean (X) = 95

standard deviation (s) = 6.6

We use the t distribution.

99% interval means 0.99 = 1 - α ; α = 0.01  

tα/2 = t0.005 = invT(0.995,29) = 2.75638

X - t a/2 * (s/√n) < μ < X + t a/2 * (s/√n)

95 - 2.75638*(6.6/√30) < μ < 95 + 2.75638*(6.6/√30)  

95 - 3 < μ < 95 + 3

92 < μ < 98

Hope this helps :)