Unit 3 Test Corrections

Twenty-one young men got a quote for the cost of a car insurance policy. The policy cost and ages of the men are shown in the scatter plot.

Select TWO statements that are true based on the scatter plot.

• Every 19-year-old in this group has a lower cost of car insurance than the 18-year-olds.

• Car insurance policy cost tends to decrease as age of the driver increases.

• The value of the correlation coefficient is very close to -1, so there is no association between age and car insurance policy cost.

• The line of best fit indicates that, in general, the cost of a car insurance policy for a 21-year-old should be, on average, about $315 less than the cost of a car insurance policy for a 20-year-old.

• The y-intercept from the line of best fit indicates that, if the linear trend holds, a car insurance policy would be $0 for a person who is about 8,897 years old.

A company that makes scarves has many different styles and colors that people can order. The company keeps track of the number of each style, color combination they make, and the average sale price for the scarves having that combination. They create a scatter plot using the data with the number of scarves along the x-axis and the average price per scarf, in dollars, along the y-axis.

• $y=-225x+1124$

• $y=-0.004x+5$

• $y=-x+5$

• $y=0.01x+5$

Kiran collects data about the number of trees on school property and the average standardized test scores for those schools. Kiran says, "The scatter plot between the number of trees on a school property and student standardized tests scores shows a strong and positive correlation. An increase in the number of trees on school property causes the students to score better on standardized tests."

What does it mean for the relationship between the variables when the correlation is strong in this situation? Pick TWO.

• The model fits the data well.

• The model does not fit the data well.

• The number of trees is a bad predictor of test scores.

• The number of trees is a good predictor of test scores.

Kiran collects data about the number of trees on school property and the average standardized test scores for those schools. Kiran says, "The scatter plot between the number of trees on a school property and student standardized tests scores shows a strong and positive correlation. An increase in the number of trees on school property causes the students to score better on standardized tests."

What does it mean for the relationship between the variables when the correlation is positive in this situation?

• As the number of trees increase, the student test scores decrease.

• As the number of trees increase, the student test scores increase.

Kiran collects data about the number of trees on school property and the average standardized test scores for those schools. Kiran says, "The scatter plot between the number of trees on a school property and student standardized tests scores shows a strong and positive correlation. An increase in the number of trees on school property causes the students to score better on standardized tests."

What is wrong with the last sentence of Kiran's statement?

• There is nothing wrong with Kiran's statement.

• An increase in trees will DECREASE student test scores.

• The change in trees does not cause a change in scores. It is not a causal relationship.

A student surveyed 100 adults who took either vitamin C, zinc, or echinacea supplements to prevent getting a cold. The adults were asked if they had a cold or no cold in the last 30 days. The results are shown in the table.

What proportion of adults in the survey took echinacea?

•  $\frac{27}{100}$  

•  $\frac{21}{100}$  

•  $\frac{6}{100}$  

•  $\frac{21}{27}$  

•  $\frac{6}{27}$  

A student surveyed 100 adults who took either vitamin C, zinc, or echinacea supplements to prevent getting a cold. The adults were asked if they had a cold or no cold in the last 30 days. The results are shown in the table.

What proportion of adults who took vitamin C reported having a cold in the last 30 days?

• $\frac{15}{26}$

• $\frac{56}{100}$

• $\frac{26}{100}$

• $\frac{15}{56}$

A student surveyed 100 adults who took either vitamin C, zinc, or echinacea supplements to prevent getting a cold. The adults were asked if they had a cold or no cold in the last 30 days. The results are shown in the table.

What proportion of adults who reported having a cold took zinc?

• $\frac{5}{17}$

• $\frac{5}{26}$

• $\frac{5}{100}$

The purchasing habits of 1,000 grocery shoppers are noted. No association is found between the variables.

How many people bought milk and did NOT buy eggs?

• 220

• 227

• 230

• 237

The purchasing habits of 1,000 grocery shoppers are noted. No association is found between the variables.

How many people did NOT buy eggs and did NOT buy milk?

• 113

• 120

• 123

• 130