SOLUTION: There are twenty multiple choice questions in an exam. Each question has four possible answers, and only one of them is correct. How can we find the probability of having 15 or mor
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-> SOLUTION: There are twenty multiple choice questions in an exam. Each question has four possible answers, and only one of them is correct. How can we find the probability of having 15 or mor
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Question 1104196: There are twenty multiple choice questions in an exam. Each question has four possible answers, and only one of them is correct. How can we find the probability of having 15 or more correct answers if a student attempts to answer every question at random. And last thing, how can we find the probability of having 5 or less correct answers? Regards... Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! use the binomial probability formula
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Probability (P) ( k successes in n trials) = nCk * p^k * (1-p)^(n-k), where nCk = n! / (k! * (n - k)!)
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for this problem p = 0.25 (probability of guessing a correct answer given 4 choices)
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P ( 15 or more correct out of 20 ) = P (15 correct out of 20) + P (16 correct out of 20) + P (17 correct out of 20) + P (18 correct out of 20) + P (19 correct out of 20) + P (20 correct out of 20) = 3.8E06
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P ( 5 or less correct out of 20 ) = P (5 correct out of 20) + P (4 correct out of 20) + P (3 correct out of 20) + P (2 correct out of 20) + P (1 correct out of 20) + P (0 correct out of 20) = 0.617 approximately 0.62
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