A.According to the International Mass Association survey, the amounts of money g

Question

A.According to the International Mass Association survey, the amounts of money girls ages 13 to 15 spend monthly are Normally distributed with the average of $31.20 and the standard deviation of $8.27. If 85 girls in this age category are randomly selected, find the probability that their average monthly shopping expense is over $32.

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C.In case a random sample of 29 TVs was chosen, find the probability that their average replacement time exceeds 3.5 years.

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E.If a random sample of 12 deliveries was selected and their standard deviation was found to be 7.87 minutes, find the probability that their average delivery time is at most 25 minutes.

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Explanation / Answer

A.According to the International Mass Association survey, the amounts of money girls ages 13 to 15 spend monthly are Normally distributed with the average of $31.20 and the standard deviation of $8.27. If 85 girls in this age category are randomly selected, find the probability that their average monthly shopping expense is over $32.

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Ans: Mean = 31.2

SD = 8.27

x = 32

z = (32 - 31.2)/8.27/85

z = 0.89

P(z > 0.89) = 0.1867

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