Suppose that a customer service center claims that the telephone calls it receives last 114 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. 114.5 seconds
B. 115.5 seconds
C. 117.5 seconds
D. 116.5 seconds

Question

Suppose that a customer service center claims that the telephone calls it receives last 114 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. 114.5 seconds
B. 115.5 seconds
C. 117.5 seconds
D. 116.5 seconds

perl · Answer

I would set up a 95% confidence interval

hockeychick23 · Answer

ok so i wrote it as, 114-1.96sqrt(81/324), did i set that up right?

perl · Answer

( 114 - 1.96 * 9 / sqrt324) , 114 + 1.96 * 9 / sqrt(324) )

perl · Answer

yes thats correct