A literature professor decides to give a 15-question true-false quiz. She wants to choose the passing grade such that the probability of passing a student who guesses on every question is less than .10. What score should be set as the lowest passing grade?
A) 11
B) 9
C) 12
D) 10

Question

Quizplus · Accepted Answer

The probability of guessing correctly on a true-false question is 1/2. The probability of guessing correctly on all 15 questions is (1/2)^15 = 1/32768. Therefore, the probability of passing a student who guesses on every question is less than .10 if the passing grade is set at 11 or higher.

A Literature Professor Decides to Give a 15-Question True-False Quiz