1. According to population data, 50 percent of Tuvans wear jump suits, while 40 percent of Tuvans wear bright orange sneakers. Moreover, wearing a jump suit and wearing bright orange sneakers are independent. What percent of Tuvans wear jump suits and bright orang sneakers?
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| a. 90 percent
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| b. 20 percent
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| c. 40 percent
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| d. 45 percent
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2. A population survey of 4 New Yorkers finds that they have, in the last year, seen the sun rise 15, 12, 16, and 20 times. The mean of this population is 15.75 (you can check if you don't believe me). What is the standard deviation of the number times a New Yorker sees the sun rise per year?
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| a. 2.86
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| b. 8.19
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| c. 3.3
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| d. 2.25
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3. A variable has a mean of 22 and a standard deviation of 7. According to the rule of thumb, what fraction of observations will lie between 8 and 36?
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| a. 79 percent.
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| b. 99 percent.
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| c. 68 percent.
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| d. 95 percent.
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4. If a variable has a positive skew, then it follows that:
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| a. The distribution has a left tail.
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| b. The distribution has a right tail.
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| c. It may have more than one mode.
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| d. The median is greater than the mean.
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5. As a measure of dispersion, the range, unlike the inter-quartile range,
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| a. can be computed for an ordered variable.
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| b. is useful for scenarios such as safety when absolute limits to dispersion are required.
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| c. can be described as "the average distance from the average."
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| d. is almost completely unaffected by outliers
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6. Suppose that bicyclists get run over on Northern Boulevard independently of each other and at a constant rate of 7 per year. What is the standard deviation of the number of bicyclists who get run over on Northern Boulevard during a given year?
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| a. 49
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| b. 2.65
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| c. 7
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| d. 3.5
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7. 10 percent of the time, the number of minutes that a customer waits in line is between 15 and 24, and 80 percent of the time it is above 24. What percent of the time is it less than 15?
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| a. 90
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| b. 10
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| c. 45
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| d. 8
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8. According to population data, 20 percent of students at Big U smoke, while 20 percent of students at Big U drink. Moreover, 10 percent of students at Big U smoke and drink. What percent of students at Big U smoke or drink?
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| a. 30
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| b. 20
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| c. 4
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| d. 40
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9. The times a Parisian has cheats on his or her spouse every month is Normally distributed with mean 20 and standard deviation 3. What is the probability that it is greater than or equal to 20.75?
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| a. 0.25
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| b. 0.4013
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| c. 0.75
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| d. 0.5987
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10. Of all teenagers, 30 percent watched television last week for 1 hours, 20 percent watched television last week for 2 hours, and 50 percent watched television last week for 5 hours. What is the mean number of hours of television that a teenager watches?
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| a. 1.07
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| b. 2.67
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| c. 3.2
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| d. 2
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11. A sample of 5 penguins finds that they have, in the last day, caught 16, 22, 17, 24, and 24 herrings. What is the mean number of herring that a penguin catches in this sample?
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| a. 20.6
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| b. 14.8
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| c. 25.75
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| d. 22
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12. A population survey of 3 flashlights finds that they last for 18, 12, and 16 minutes. The mean of this population is 15.33 (you can check if you don't believe me). What is the variance of the number of minutes that a flashlight lasts?
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| a. 2.49
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| b. 6.22
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| c. 2.22
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| d. 9.33
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13. The cumulative distribution function of the number of papers that a bureaucrat stamps in an hour includes the values F(11) = 0.1, F(16) = 0.15, and F(24) = 0.2. What is the probability that the variable will be greater than 16?
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| a. 0.15
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| b. 0.7
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| c. 0.85
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| d. 0.3
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14. 19 precious little children are playing in a park. Emily's 2 children are among them. Suddenly, a pit bull comes along and mauls 2 of the children. If the pit bull is equally likely to have chosen any 2 children in any order, what is the probability that the dog mauled Emily's oldest child first, followed by her youngest child?
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| a. One in 361.
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| b. One in 38.
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| c. One in 342.
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| d. One in 171.
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15. Population data tell us that 53 percent of talking dolls are ugly. Suppose that we take independent samples of talking dolls of size 7. Then, the variance of the number of dolls that are ugly in each sample is:
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| a. 1.74
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| b. 3.71
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| c. 3.5
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| d. 1.32
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16. As a measure of central tendency, the median, unlike the mean,
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| a. will always change if one observation changes value.
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| b. can be used with quantitative or ordered variables, but not category variables.
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| c. only exists for caregory variables.
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| d. is unique for any quantitative variable.
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17. A sample of 3 serial killers finds that they have, in the last year, murdered 13, 16, and 20 victims. The mean of this sample is 16.33 (you can check if you don't believe me). What is the mean absolute deviation of the number of victims that a serial killer murders in a year?
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| a. 12.33
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| b. 3.51
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| c. 3.66
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| d. 2.44
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18. 18 old coins are sitting on a table. 2 of them are pre-World-War II pennies of different vintages. I pick 2 coins from the table without looking. If I am equally likely to pick any 2 coins, what is the probability that I pick the 2 old pennies?
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| a. One in 153.
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| b. One in 324.
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| c. One in 36.
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| d. One in 306.
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19. According to population data, 30 percent of commuters on the A train are tired, while 40 percent of commuters on the A train have a seat. Moreover, 15 percent of commuters on the A train are tired and have a seat. What is the probability that a commuter on the A train is tired, given that he or she has a seat?
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| a. 12 percent
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| b. 50 percent
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| c. 37.5 percent
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| d. 15 percent
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20. A sample of 10 students finds that they have, in the last month, seen 21, 25, 17, 19, 23, 18, 24, 19, 17, and 17 movies. What is the modal number of movies a student has seen in the last month in this sample?
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| a. 9.33
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| b. 19
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| c. 20
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| d. 17
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