AP Stats Random Variables

Which of the following is the best estimate of the standard deviation of the distribution in the figure?

• 18

• 9

• 54

• 97

• 106

A company determines the mean and standard deviation of the employees' salaries in one year. What is the best description of the standard deviation?

• Approximately the median distance between the individual salaries of employees and the mean of every employee's salary.

• The amount of money separating the highest salary from the lowest salary when considering the middle 50% of the distribution.

• The amount of money separating the highest salary from the lowest salary when considering all employees.

• The distance between the salary of an employee and the mean salary of all the employees.

• Approximately the mean distance between the individual salaries of employees and the mean of all employees' salaries.

The heights of adult women are approximately normally distributed about a mean of 65 inches with a standard deviation of 2 inches. If Bella is at the 87th percentile in height for adult women, then her height, in inches, is closest to

• 63

• 67

• 66

• 72

• 70

Andrea's doctor told her that the standardized score (z-score) for her systolic blood pressure, as compared to the blood pressure of other women her age, is 1.75. Which of the following is the best interpretation of this standardized score?

• Andrea's systolic blood pressure is 175.

• Andrea's systolic blood pressure is 1.75 standard deviations above the average systolic blood pressure of women her age.

• Andrea's systolic blood pressure is 1.75 above the average systolic blood pressure of women her age

• Only 1.75% of women Andrea's age have a higher systolic blood pressure than she does.

• Andrea's systolic blood pressure is 1.75 times the average systolic blood pressure of women her age.

In a certain school, students can choose whether to eat in the school’s cafeteria. A reporter working for the school’s newspaper polled students on their reactions to changes in the menu at the cafeteria. For each student leaving the cafeteria in one 20-minute time period, the reporter used a die to determine whether to stop the student and ask how he or she felt about the new menu. In the reporter’s article it was stated that a random sample of the students showed that 23% of the school’s student population was happy with the new menu. Which of the following statements is true?

• Because each student leaving the cafeteria was randomly selected and could choose to answer or not, this is a random sample of the student population, and the 23% is an accurate measurement of the school population’s view of the new menu.

• Because students self-selected whether to eat in the cafeteria, the sampling method might be biased and the sample might not be representative of all students in the school.

• The survey would have been more effective if the reporter had collected the data in one 10-minute time period rather than in one 20-minute time period.

• The survey would have been more effective if students who cared about the food could have called the reporter to tell how they felt about the new menu, so that only students with opinions on the subject would have been surveyed.

• Because no treatment was imposed on the students eating in the cafeteria, one cannot make any conclusions about the new menu.

The boys and girls basketball teams at a high school had their heights measured at practice. The following data was recorded for their heights. What can you conclude from the distributions?

• The girls have a larger median and a larger range in heights.

• The boys had a smaller median height than the girls; however, the boys had a larger range of heights.

• The median height for the boys and the girls is the same; however, the girls have a larger range.

• The median height for the boys is larger; however, the girls have a larger range.

• No information can be concluded from the distribution since there is no key included.

The equation of the LSRL for the points on a scatterplot is ŷ = 5.3-0.23x. What is the residual for the point (5, 4)?

• -0.15

• 0.15

• 1

• 0.62

• 0.85

A cosmetics supplier ships boxes of highlighter to individual customers. The distribution of weights of shipped boxes is approximately normal with mean 5 pounds and standard deviation 1.2 pounds. Which expression represents the weight, in pounds, at the 75th percentile of the distribution?

• -1.96(1.2) + 5

• -0.25(1.2) + 5

• 0.25(1.2) + 5

• 0.67(1.2) + 5

• 0.75(1.2) + 5

The boxplots summarize two data sets, 1 and 2. Which of the following must be true?

• I only

• I and III only

• I and II only

• I, II, and III

• III only

What's the appropriate interpretation of the slope of the regression line?

• For every additional 0.61 hours of growth, the culture is predicted to weight 1 more gram.

• For every additional hour of growth, the culture is predicted to weigh 0.61 more grams.

• For every additional hour of growth, the logarithm of the culture's weight in grams is predicted to increase by 0.61.

• At the beginning of the experiment, the logarithm of the culture's weight in grams was approximately 0.61 ounces.