An analysis of the grades on the first test in History 101 revealed that they approximate a normal curve with a mean of 75 and a standard deviation of 8. The instructor wants to award the grade of A to the upper 10 percent of the test grades. What is the dividing point between an A and a B grade?
A) 80
B) 85
C) 90
D) 95

Question

Quizplus · Accepted Answer

To find the dividing point between an A and a B grade, we need to find the score that corresponds to the top 10% of the distribution.

Using a z-table or calculator, we find that the z-score that corresponds to the top 10% of the distribution is approximately 1.28.

We can use the formula:

z-score = (X - mean) / standard deviation

to solve for the corresponding test score (X).

1.28 = (X - 75) / 8

Solving for X, we get:

X = 85

Therefore, the dividing point between an A and a B grade is 85.

An Analysis of the Grades on the First Test in History