Question

Suppose that a customer service center claims that the telephone call it receives last 112 seconds on average, with a standard deviation of 9 seconds. If you took a sample of 324 telephone calls, which of the following mean times would be within the 95% confidence interval?

A. 115.5 seconds
B. 112.5 seconds
C. 114.5 seconds
D. 113.5 seconds

Answer 1

@ganeshie8

Answer 2

margin of error = 1.96*9/sqrt(324) = 0.98

so the confidence interval is\[\large (112-0.98, 112+0.98) = (111.02, 112.98 )\]

Answer 3

look at the options and pick the one that lies in that interval

Answer 4

so it would be 112.5?

Answer 5

Yep!

Answer 6

Thanks a lot!

Answer 7

yw