Question

A popular restaurant advertises that it delivers its orders within 30 minutes. Suppose the average delivery time for one store is 27 minutes with a standard deviation of three minutes. One particular order delivery has a z-score of –2.15. Which of the following statements is not a correct interpretation?
A.The delivery time was 2.15 standard deviations below the average delivery time.
B.The delivery time was less than the average delivery time by 2.15 standard deviations.
C.The delivery time was faster than the average delivery time by 2.15 standard deviations.
D.The delivery time was slower than the average delivery time by 2.15 standard deviations.

Answer 1

Answer: B. The delivery time was less than the average delivery time by 2.15 standard deviations.

Step-by-step explanation:

Given: A popular restaurant advertises that it delivers its orders within 30 minutes.

Suppose the average delivery time for one store is 27 minutes with a standard deviation of 3 minutes.

z-score value represents the number of standard deviations is the data value is far from mean.

Here, z-score = -2.15 which clearly indicates that the delivery time was 2.15 standard deviations below( '-' sign suggest value is below mean) the average delivery time.

Hence, the correct option is B.