Bill has completed a 10-question multiple choice test on which he answered 7 questions correctly. Each question had one correct answer to be chosen from five alternative. Bill says that he answered the test by randomly guessing the answers without reading the questions or answers.
a. Define the random variable x to be the number of correct answers on this test, and construct the probability distribution if the answers were obtained by random guessing
b. what is the probability that bill guessed 7 of the 10 correctly?
c. what is the probability that anybody can guess six or more answers correctly?
d. Do yo believe that bill actually randomly guessed as he claims. Explain?