A history professor decides to give a 12-question true-false quiz. She wants to choose the passing grade suchthat the probability of passing a student who guesses on every question is less than 0.10. What score should beset as the lowest passing grade?
A) 9
B) 7
C) 10
D) 8

Question

Quizplus · Accepted Answer

The probability of guessing correctly on a true-false question is 0.5. Using the binomial distribution, we calculate the probability of getting at least 9 correct answers out of 12 by guessing. The cumulative probability of getting 9, 10, 11, or 12 correct answers is less than 0.10, making 9 the lowest passing grade.

A History Professor Decides to Give a 12-Question True-False Quiz