Question

A random sample of 35 UCF students has a mean electricity bill of $115. Assume the population standard deviation is $18.10. Construct a 90% confidence interval for the mean electricity bill of all UCF students. Round final answer to two decimal places.

Answer 1

Answer:

Step-by-step explanation:

confidence interval formula is epressed as;

CI = xbar ± z(s/√n)

xbar is the mean = $115

z is the z score at 90% CI = 1.645

s is the standard deviation = 18.10

n is the sample size = 35

Substitute;

CI = 115 ± 1.645(18.10/√35)

CI = 115 ± 1.645(3.0594)

CI = 115± 5.0328

CI = (115-5.0328, 115+5.0328)

CI = (109.97, 120.03)

Hence a 90% confidence interval for the mean electricity bill of all UCF students is 109.97<x<120.03