Professor Elderman has given the same multiple-choice final exam in his Principles of Microeconomics class for many years. After examining his records from the past 10 years, he finds that the scores have a mean of 76 and a standard deviation of 12. Professor Elderman offers his class of 36 a pizza party if the class average is above 80. What is the probability that he will have to deliver on his promise?
A) 0.0228
B) 0.3707
C) 0.6293
D) 0.9772

Question

Quizplus · Accepted Answer

The probability that the class average is above 80 can be found using the standard normal distribution. The standard error of the mean is 12/sqrt(36) = 2. The z-score for a class average of 80 is (80-76)/2 = 2. The probability of a z-score greater than 2 is 0.0228.

Professor Elderman Has Given the Same Multiple-Choice Final Exam in His