The observed times (in minutes) it takes a runner to complete a marathon are normally distributed. The z-score for his running time this week is –2. Which one of the following statements is a correct interpretation of his z-score?
(A)This week his time was two minutes lower than his time last week. (B)This week his time was two minutes lower than his best time ever. (C)This week his time was two minutes lower than his average time. (D)This week his time was two standard deviations lower than his average time.
D