Question 2 According to a report by Scarborough Research, the average monthly ho
ID: 2706245 • Letter: Q
Question
Question 2
According to a report by Scarborough Research, the average monthly household cellular phone bill is $73. Suppose local monthly household cell phone bills are normally distributed with a standard deviation of $11.35.
a. What is the probability that a randomly selected monthly cell phone bill is more than $100?
b. What is the probability that a randomly selected monthly cell phone bill is between $60 and $83?
c. What is the probability that a randomly selected monthly cell phone bill is between $80 and $90?
d. What is the probability that a randomly selected monthly cell phone bill is no more than $55?
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Explanation / Answer
According to a report by Scarborough Research, the average monthly household cellular phone bill is $73. Suppose local monthly household cell phone bills are normally distributed with a standard deviation of $11.35.a. What is the probability that a randomly selected monthly cell phone bill is more than $100?
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z(100) = (100-73)/11.35 = 27/11.35 = 2.3789
P(x > 100) = P(z > 2.3789) = 0.0087
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b. What is the probability that a randomly selected monthly cell phone bill is between $60 and $83?
z(83) = (83-73)/11.35 = 10/11.35 = 0.8811
z(60) = (60-73)/11.35 = -1.145
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P(60< x <83) = P(-1.145< z < 0.8811) = 0.6848
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Use the same methods to work "C" and "D".
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