On the first test of material on dinosaurs, a class of sixth graders had a mean score of 36 with S = 12. The teacher was disappointed and assigned six pages of homework on dinosaurs and scheduled a second test. The top one-fourth of the class studied the extra material and did even better on the second test. The other three-fourths ignored the material and made the same score as before. Pick the mean and standard deviation that might be found, given the description.
A) $\bar { X }$ = 36 S = 12
B) $\bar { X }$ =36S=18
C) $\bar { X }$ = 42 S = 18
D) $\bar { X }$ = 42 S = 12.

Question

Quizplus · Accepted Answer

The top one-fourth of the class improved their scores, which would increase the mean, but since three-fourths of the class scored the same, the variation in scores would also increase, making option C the most likely with an increased mean and standard deviation.

On the First Test of Material on Dinosaurs, a Class Xˉ\bar { X }Xˉ

On the First Test of Material on Dinosaurs, a Class $\bar { X }$