From past history, the scores on a statistics test are normally distributed with a mean of 70% and a standard deviation of 5%. To earn an "A" on the test, a student must be in the top 5% of the class. What should a student score to receive an "A"?
A) 80.84
B) 75.49
C) 78.2
D) 76.90

Question

Quizplus · Accepted Answer

To be in the top 5%, the z-score must be equal to or greater than 1.645. Using the formula z = (x - μ) / σ, we can solve for the score necessary to achieve this z-score:
1.645 = (x - 70) / 5
x = 78.2. Therefore, a student must score at least 78.2% on the test to receive an "A."

From Past History, the Scores on a Statistics Test Are