Question 923600: Assume that on a standardized test of 100 questions, a person has a probability of 80% of answering any particular question correctly. Find the probability of answering between 70 and 80 questions, inclusive, correctly.
P(70 ≤ X ≤ 80)=?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Assume that on a standardized test of 100 questions, a person has a probability of 80% of answering any particular question correctly. Find the probability of answering between 70 and 80 questions, inclusive, correctly.
P(70 ≤ X ≤ 80)=?
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mean = np = 100*0.8 = 80
std = sqrt(npq) = sqrt(80*0.20) = 4
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z(70) = (70-80)/4 = -5/2
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z(80) = 0
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P(7<= x <=80) = P(-5/2)<= z <= 0) = 0.49
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Cheers,
Stan H.
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