Give your answer to the one decimal place

Question

If n=31, (x-bar)=36, and s=15, construct a confidence interval at a 99% confidence level. Assume the data came from a normally distributed population.

Answer 1

CI = x-bar +/- t-critical * s/square root(n)

t-critical for 99% confidence level, is t-value at upper tail of 0.005 and 31-1=30 degrees of freedom = 2.75

CI = 36 +/- 2.75 * 15/square root(31) = 7.41

= 36 +/- 7.41 = (28.59,43.41)