Question

A mathematics teacher gives a test with seven extremely difficult multiple choice questions. Each question has 5 possible answers.You have no idea what the correct answers are, so you randomly guess the answer to each question. Use an appropriate probability distribution to determine the probability that you will pass the test (over 50%).

Answer 1

Let X denote the number of correct answers.

Then X follows a Binomial with n=7 and p =(1/5) = 0.2.

We need to find P(X>=4).

P(X>=4) = 1-P(X<=3) = 1- 0.9667 = 0.0333 (ans)