The quiz grades of a math class are given. 83, 76, 68, 97, 68, 80, 89, 74, 75, 81, 91, 90 The grades are normally distributed with a mean of 81 and a standard deviation of 9.3. What is the z-score of the highest grade in the quiz?

A) - 1.72

B) - 1.08

C) 1.08

D) 1.72

the answer is c) 1.08

Step-by-step explanation:

Step1:

Formula for calculating z-score is;

Z = (x-mean) / standard deviation

where x is the value for which z-score is required

Step 2:

As asked in the question z-score for highest grade is required which is 91;

z = (91-81) / 9.3

z=10/9.3

z=1.075

which is approximately;

z=1.08