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