Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 7

Question 1

A news headline reads: 'Students who eat lunch perform better in afternoon classes.' The data came from a study where students chose whether to eat lunch.
Which of the following is most likely a confounding variable?

Accepted Answer

Overall health and family habits that affect both eating patterns and academic performance

Answer

The type of food served in the cafeteria

Answer

The time of day the afternoon classes are scheduled

Answer

The grade level of the students

Question 2

A pharmaceutical company randomly assigns 1,000 patients with high blood pressure to either a new medication or a placebo. After 6 months, the medication group shows a significant reduction in blood pressure. The company claims the medication is effective for all patients with high blood pressure. What is the most valid concern?

Accepted Answer

The study sample may not represent all patients with high blood pressure, such as those with other conditions.

Answer

Placebos are never appropriate in blood pressure studies.

Answer

Blood pressure cannot be measured accurately in randomized trials.

Answer

The 6-month period is too long for a blood pressure study.

Question 3

Researchers observe that countries with more hospitals per capita also have longer life expectancy. They conclude that building more hospitals increases life expectancy. What is the most likely confounding variable?

Accepted Answer

National wealth, which increases both hospital capacity and access to food, education, and clean water

Answer

The number of doctors per hospital

Answer

Geographic size of the country

Answer

The age distribution of each country's population

Question 4

A social scientist conducts an experiment by randomly assigning rural communities to receive a new community center and comparing crime rates to communities that did not receive one. After 2 years, crime rates are lower in communities with the center. What is the scope of the valid causal conclusion?

Accepted Answer

In rural communities similar to those studied, community centers likely cause lower crime rates.

Answer

Community centers cause lower crime rates in all cities globally.

Answer

Crime rates would have dropped even without the community centers.

Answer

There is only a correlation, not a causal relationship, between centers and crime.

Question 5

A study surveys 800 teenagers about sleep habits and academic performance. Students who sleep 9 or more hours have higher GPA. A parent concludes that forcing teens to sleep 9 hours will improve their grades. Why is this conclusion flawed?

Accepted Answer

The association is from an observational study; factors like family structure and health may cause both more sleep and higher GPA.

Answer

GPA is not a good measure of academic performance.

Answer

Teenagers cannot control their sleep schedules.

Answer

The survey sample of 800 is too small to draw conclusions.

Question 6

Two researchers study the effect of tutoring on test scores. Researcher A randomly assigns students to tutoring or no tutoring. Researcher B surveys students who chose to get tutoring vs. those who didn't. Which researcher can draw causal conclusions, and why?

Accepted Answer

Researcher A, because random assignment controls for confounding variables.

Answer

Researcher B, because voluntary participation increases motivation.

Answer

Both researchers, because both measure tutoring and test scores.

Answer

Neither researcher, because test scores have too many influences.

Question 7

A report states: 'Among 500 randomly selected adults, those who meditate have lower cortisol levels.' A journalist writes: 'Meditation reduces cortisol.' What is wrong with the journalist's conclusion?

Accepted Answer

The study used a random sample but did not randomly assign participants to meditate, so causation cannot be concluded.

Answer

Cortisol levels cannot be measured in a sample of 500.

Answer

The journalist should have reported the confidence interval for cortisol levels.

Answer

A random sample is not appropriate for studying meditation habits.