Question

Two students taking a multiple choice exam with 20 questions and four choices for each question have the same incorrect answer on eight of the problems. The probability that student B guesses the same incorrect answer as student A on a particular question is 1/4. If the student is guessing, it is reasonable to assume guesses for different problems are independent. The instructor for the class suspects the students exchanged answers. The teacher decides to present a statistical argument to substantiate the accusation. A possible model for the number of incorrect questions that agree is:

Answer 1

The possible model for the number of incorrect questions that agree is a binomial distribution. The teacher can use this model to calculate the probability of observing 8 or more agreed-upon answers.

Step-by-step explanation:

The possible model for the number of incorrect questions that agree is a binomial distribution because there are a fixed number of trials (the number of questions) and each trial has two possible outcomes (agree or disagree).

The probability that student B guesses the same incorrect answer as student A on a particular question is 1/4, so the probability of agreeing on a particular question is 1/4. Since there are 20 questions, the probability that they agree on exactly 8 questions is given by the binomial probability formula: P(x = 8) = C(20, 8) * (1/4)^8 * (3/4)^12.

The teacher can use this model to calculate the probability of observing 8 or more agreed-upon answers by summing the probabilities of all possible outcomes with 8 or more agreed-upon answers: P(x ≥ 8) = P(x = 8) + P(x = 9) + ... + P(x = 20).

Answer 2

The Possible model is binomial distribution model.

Step-by-step explanation:

The argument that both students cheated in the exam can be proved by a hypothesis that both the students got the same answers incorrectly.

The same incorrect answers prove that both students have cheated on the test.

Therefore the sample of incorrect answers is, n = 8

Thus, the success probability, P = 0.25

Since the given condition has only two outcomes that are choosing the same answer or not choosing the same answer. Thus, this can be solved by the binomial distribution model.

So, binomial distribution with n = 8 and p = 0 .25.