Question 855562: A student is taking a multiple choice exam in which each question has five choices. Assuming
that she has no knowledge of the correct answers to any of the questions, she has decided on a
strategy in which she will place five balls (marked A, B, C, D, E) into a box. She randomly selects
one ball for each question and replaces the ball in the box. The marking on the ball will determine
her answer to the question.
There are four multiple choice questions on the exam.
(a) What is the probability that she will obtain full marks?
(b) What is the probability that she will get at least three questions correct?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A student is taking a multiple choice exam in which each question has five choices. Assuming
that she has no knowledge of the correct answers to any of the questions, she has decided on a
strategy in which she will place five balls (marked A, B, C, D, E) into a box. She randomly selects
one ball for each question and replaces the ball in the box. The marking on the ball will determine
her answer to the question.
There are four multiple choice questions on the exam.
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Binomial Problem with n = 4 and p(correct) = 1/5
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(a) What is the probability that she will obtain full marks?
P(x = 4) = (1/5)^4 = 0.0016
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(b) What is the probability that she will get at least three questions correct?
P(3<= x <=5) = 1 - binomcdf(4,1/5,2) = 0.0272
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Cheers,
Stan H.
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