Question 821846
The test contains 100 multiple-choice questions. Each question has 5 possible answers, only one of which is the correct answer.
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Binomial with n = 100 and p(correct) = 1/5 
What are John’s chances of scoring: 
a. exactly 70 on the exam?
P(x = 70) = 100C70(1/5)^70*(4/5)^30 = binompdf(100,1/5,70) = 4.29x10^-27
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b. 70 or better on the exam?
P(70<= x <=100) = 1 - binomcdf(100,1/5,69) = 0 to 9 decimal places
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c. 90 or better on the exam?
P(90<= x <=100) = 1 - binomcdf(100,1/5,89) = 0 to 9 decimal places
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Cheers,
Stan H.
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