Data Set 1:

2,4,6,8

For data Set 1,what is the Z-score for X = 6? (Use for standard deviation)

George took four exams in American history. On each, he made a score of 89. The 's and 's for these four tests are given below. On which test did George's 89 represent his best performance?

A. = 95, = 6

B. = 95, = 12

C. = 92, = 2

D. = 91, = 1

If you could please help me better understand this , thank you!