Measures of the Spread of the Data · Exercise 21

An elementary school class ran one mile with a mean of 11 minutes and a standard deviation of three minutes. Rachel, a student in the class, ran one mile in eight minutes. A junior high school class ran one mile with a mean of nine minutes and a standard deviation of two minutes. Kenji, a student in the class, ran one mile in 8.5 minutes. A high school class ran one mile with a mean of seven minutes and a standard deviation of four minutes. Nedda, a student in the class, ran one mile in eight minutes.

(a) Why is Kenji considered a better runner than Nedda even though Nedda ran faster than he?
(b) Who is the fastest runner with respect to his or her class? Explain why.

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Statistics · §2.7 Measures of the Spread of the Data · Exercise 21