Keenan scored 80 points on an exam that had a mean score of 77 points and a standard deviation of 4.9 points. Rachel scored 78 points on an exam that had a mean score of 75 points and a standard deviation of 3.7 points. It is meaningless to compare Keenan’s and Rachel’s scores directly, because they each took a different exam. Which of the following describes a valid way to use statistics to compare Keenan’s score on his exam with Rachel’s score on her exam?

Group of answer choices

Keenan did equally as well as Rachel because each of them scored 3 points above the mean for their exam.

Keenan did better than Rachel because his exam had a greater standard deviation than Rachel's had.

Rachel did better than Keenan because her z-score was greater than Keenan's.

Rachel did better than Keenan because the mean for her exam was less than the mean for Keenan's exam.