You are working as a quality control manager for FedEx and are responsible for d

Question

You are working as a quality control manager for FedEx and are responsible for delivery time customer satisfaction. Historically, the worldwide average delivery time is 15.14 days with a standard deviation of 2.794 days. You select 59 random deliveries over the course of a few months. Given your historical parameters still hold true, what is the probability that the average time until delivery is between 14.82 and 15.14 days?

1) 0.6897

2) 0.3103

3) The sample mean will never fall in this range.

4) 0.3513

5) 0.0456

Suppose you are interested in measuring the amount of time, on average, it takes you to make your commute to school. You've estimated that the average time is 37.56 minutes with a standard deviation of 6.303 minutes. Over 10 random days, you measure your commute time. Assuming that your estimated parameters are correct, what is the probability that the average commute time over that 10 day period is between 37.56 and 37.6 minutes?

1) -<0.0001

2) 0.0080

3) 0.0025

4) 1.0080

5) The sample mean will never fall in this range.

Explanation / Answer

1)

option (2) is correct

2)

option (2) is correct

for normal distribution z score =(X-)/ here mean=       = 15.140 std deviation   == 2.794 sample size       =n= 59 std error=x=/n= 0.3637

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