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The average (arithmetic mean) number of passengers on a
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24 Nov 2017, 20:47
24 Nov 2017, 20:47
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Question Stats:
81% (00:42) correct
18% (01:03) wrong based on 38 sessions
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The average (arithmetic mean) number of passengers on a subway car is 60. If the number of passengers on a car has a normal distribution with a standard deviation of 20, approximately what percent of subway cars carry more than 80 passengers?
A. 16%
B. 48%
C. 68%
D. 88%
E. 98%
A. 16%
B. 48%
C. 68%
D. 88%
E. 98%
Drill 1
Question: 11
Page: 523
Question: 11
Page: 523
Re: The average (arithmetic mean) number of passengers on a
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10 Dec 2017, 17:13
10 Dec 2017, 17:13
1
Expert Reply
Explanation
Adding the standard deviation (20) to the mean (60) gives you the number of passengers in a car that carries exactly one standard deviation above the mean number of passengers (80).
The first standard deviation above the mean represents 34% of the population in a normal distribution, and a further 50% falls below the mean, so 84% of the cars will carry 80 people or fewer. Subtracting this from the entire population (100%) gives you the percent of cars that carry greater than 80: 100% − 84% = 16%.
The answer is choice A.
Adding the standard deviation (20) to the mean (60) gives you the number of passengers in a car that carries exactly one standard deviation above the mean number of passengers (80).
The first standard deviation above the mean represents 34% of the population in a normal distribution, and a further 50% falls below the mean, so 84% of the cars will carry 80 people or fewer. Subtracting this from the entire population (100%) gives you the percent of cars that carry greater than 80: 100% − 84% = 16%.
The answer is choice A.
Re: The average (arithmetic mean) number of passengers on a
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30 Sep 2023, 21:30
30 Sep 2023, 21:30
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