Logge MATHEMATICAL ASSOCIATION OF AMERICA webwork/mat 221 fal 2017/ch5 sec3/9 Ch

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Logge MATHEMATICAL ASSOCIATION OF AMERICA webwork/mat 221 fal 2017/ch5 sec3/9 Ch5 Sec3: Problem 9 Previous Problem List Next t point) Use nomal approximation (without continuity cormection) to estimate the probability of passing a true/taise test of 30 questions if the minimum ang grade is 70% and all responses are random guesses. Preview My Answers Submit Arswers You have attermpted this problem 0 times You have unlimited attempts remaining Email instructor Page generated a 11/0O/2017 at 08:10pm EST

Explanation / Answer

p = 0.5
n = 30

mean = np = 0.5*30 = 15
std.dev. = sqrt(npq) = sqrt(30*0.5*0.5) = 2.7386

70% means 30*0.7 = 21 or more to be correct

P(X > 21) = P(z > (21 - 15)/2.7386) = P(z > 2.1909) = 0.0142

Hence required probability = 0.0142

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