AP Statistics Unit 3 Review

• A. Control of known sources of variability
• Random selection of subjects
• Random assignment of subjects to treatments
• Replication on a sufficient number of subjects

• I only
• II only
• III only
• I and III only

• Sample Survey
• Census
• Observational Study
• Simulation

• I only
• I and II only
• I and III only
• II and III only

• I only
• II only
• III only
• II and III only

• bias.
• confounding. 
• undercoverage.
• variation.

Rani went around the laboratory where she works and measured her coworkers' ear circumference (in millimeters). Then she matched her results with each coworkers' age and created the following scatterplot and regression line. The fitted line has a slope of 0.48. What is the best interpretation of this slope?

• On average, each 1 year increase in age was associated with a 0.48 millimeter increase in ear circumference.

• On average, each 1 millimeter increase in ear circumference was associated with a 0.48 year increase in age.

• We would predict a person who is 0 years old to have an ear circumference of 0.48 mm.

• We would predict a person who is 0 years old to have an ear circumference of 90 mm.

The scatterplot and regression line below show the relationship between the percentage of American adults who smoke and years since 1945.

The fitted line has a y-intercept of 41.

What is the best interpretation of this y-intercept?

• In 1945, approximately 0 %, of American adults were smokers.

• The model indicates that 41% of American adults smoked in 1945.

• 41% of American adults smoke.

• The model indicates that approximately 41% of American adults smoked in 1985.

Baruti, a ranger in Kruger National Park in South Africa, collected data about the elephant population in the park. She compared the foot lengths of the elephants and their shoulder height (both in centimeters) and created the following scatterplot and regression line. The fitted line has a slope of 5.89. What is the best interpretation of this slope?

• On average, each 1 centimeter increase in foot length was associated with a 5.89 centimeter increase in shoulder height.

• On average, each 1 centimeter increase in shoulder height was associated with a 5.89 centimeter increase in foot length.

• We would predict an elephant with a foot length of 0 centimeters to have a shoulder height of 5.89 centimeters.

• We would predict an elephant with a foot length of 0 centimeters to have a shoulder height of 0 centimeters.

Camille's math test included a survey question asking how many hours students spent studying for the test. The scatterplot and regression line below show the relationship between how many hours students spent studying and their score on the test. The fitted line has a y-intercept of 37. What is the best interpretation of this y-intercept?

• The model predicts that the study time will increase 37 hours for each additional point scored.

• The model predicts that the score will increase 37 points for each additional hour of study time.

• The model predicts that a student who scored 0 points studied for 37 hours.

• The model predicts that students who didn't study at all will have an average score of 37 points.