A test has 6 multiple choice questions,each with 4 alternatives.What is the probability of guessing 5 or more questions correctly?
A).5340
B).4660
C).9954
D).0046

Question

Quizplus · Accepted Answer

The probability of guessing a question correctly is 1/4. Using the binomial probability formula, calculate the probability of getting exactly 5 and exactly 6 questions correct, then sum these probabilities. The probability of getting 5 correct is 6C5 * (1/4)^5 * (3/4)^1 and for 6 correct is 6C6 * (1/4)^6. Adding these gives approximately 0.0046.

A Test Has 6 Multiple Choice Questions,each with 4 Alternatives