Nationwide, the average waiting time until a electric utility customer service r

Question

Nationwide, the average waiting time until a electric utility customer service representative answers a call is 300 seconds per call. The Gigantic Kilowatt Energy Company took a sample of 35 calls and found that, on the average, they answered in 240 seconds per call with a standard deviation of 50. Can the company claim that they are faster than the average utility?

A) No, because –0.20 falls in the critical region
B) Yes, because –7.10 falls in the critical region
C) No, because –1.20 falls in the critical region
D) Yes, because –0.20 falls in the critical region

Explanation / Answer

z = (240-300)/[50/sqrt(35)] = -7.10 B

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