Seat belts are supposed to save lives. Here are the results of a 1988 study of accident records conducted by the Florida State Department of Highway Safety. The researchers classified people in vehicles involved in accidents as having worn seat belts or not.

The following two-way table gives the results of the study:

412,368	510	412,878
162,527	1,601	164,128
574,895	2,111	577,006

In this example, it would be appropriate to calculate:

the five-number summary of both variables the correlation coefficient r conditional column percentages conditional row percentages none of the above

Question 2 of 8Points: 10

A local ice cream shop kept track of the number of cans of cold soda it sold each day, and the temperature that day, for two months during the summer. The data are displayed in the scatterplot below:

The one outlier corresponds to a day which was a holiday and the shop had an unusually high volume of customers. Which of the following is true?

If the temperature were measured in degrees Celsius (C = 5/9 * (F - 32)), the value of r would change accordingly. A reasonable value of the correlation coefficient r for these data is 1.3. If the outlier were removed, r would get closer to -1. If the outlier were removed, r would get closer to 1. If the outlier were removed, r would get closer to 0.

Question 3 of 8Points: 10

Suppose that the correlation r between two quantitative variables was found to be r = 0. This means that:

There is no relationship between the two variables. There is a strong relationship between the two variables. There is no linear relationship between the two variables. There is a strong linear relationship between the two variables. None of the above.

Question 4 of 8Points: 10

A correlation of r = .79 is found between the number of burglaries and the number of police employed by a city. Which of the following is true?

Burglaries must be the cause of more police. There is a pretty strong positive linear relationship between number of burglaries and number of police. Population size of the city is a possible lurking variable that is behind this relationship. Both (B) and (C) are true. None of the above.

Question 5 of 8Points: 10

The data in the scatterplot below are an individual's driving experience in years and that individual's monthly auto insurance premium in dollars. The o's correspond to females and the +'s to males.

Which of the following conclusions is most accurate?

There is a positive correlation between gender and years of experience, since men tend to have more. There is a positive correlation between monthly auto premiums and years of experience for males and for females. There is a negative correlation between monthly auto premiums and years of experience for males and for females. Both (A) and (B) are correct. Both (A) and (C) are correct.

Question 6 of 8Points: 10

What can we say about the relationship between the correlation r and the slope b of the least-squares line for the same set of data?

both r and b always have values between -1 and 1 b is always larger than r r is always larger than b the slope b is always equal to the square of the correlation r r and b are both positive or both negative

Question 7 of 8Points: 10

A study was done on the batting averages for two baseball players: Hitmore and Bunter. Data were collected over a period of time for baseball parks that are natural and artificial turf. It was found that Hitmore does better overall (i.e., has a better batting average). However, for both natural and artificial turf separately, Bunter does better.

Which of the following is correct?

This is an example of a negative association between variables. This is an example of Simpson's Paradox. "Turf" is a lurking variable in this example. Both (B) and (C) are correct. This situation is mathematically impossible.