Question

Hello, my problem is I have a random sample of only 15 sales average is $115 with a known population standard deviation of $25.00. Obtain a 92% confidence interval and explain what your answer means. I am not sure what to do because the sample size is only 15. Thanks for your help.

Answer 1

mean = $115
Sd = $25
n = 15
1-a = .92

a = 0.08
Za/2 = z.04 = 1.75

115 -+ 1.75 * 25/sqrt15))

115-+ 11.296

(103.704, 126.296)

Answer 2

Thank you, I got the same answer, but I thought that because the sample size was less than 30, there was something I missed.