According to a report by Scarborough Research, the average monthly household cellular phone bill is $73....

According to a report by Scarborough Research, the average monthly household cellular phone bill is $73. Suppose local monthly household bills are normally distributed with a standard deviation of $11.35.

(a) What is the probability that a randomly selected monthly cellphone bill is between $60 and $74?

(b) What is the probability that a randomly selected monthly cellphone bill is between $79 and $88?

Solutions

Expert Solution

Let X be a randomly selected monthly cellphone bill. We know that X is normally distributed with mean and standard deviation

(a) What is the probability that a randomly selected monthly cellphone bill is between $60 and $74?

ans: the probability that a randomly selected monthly cellphone bill is between $60 and $74 is 0.4108

(b) What is the probability that a randomly selected monthly cellphone bill is between $79 and $88?

ans: the probability that a randomly selected monthly cellphone bill is between $79 and $88 is 0.2046

ans: the probability that a randomly selected monthly cellphone bill is no more than $39 is 0.0013

orchestra answered 1 year ago

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