Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 2

Question 1

Researchers want to determine whether a new tutoring program improves standardized test scores.
They randomly assign 150 students to receive tutoring and 150 students to a control group with no tutoring, then compare scores.
Why is random assignment important in this study?

Accepted Answer

It controls for confounding variables by balancing them across groups on average.

Answer

It ensures all students have an equal chance of being surveyed.

Answer

It guarantees the tutoring group will show improvement.

Answer

It increases the sample size, reducing the margin of error.

Question 2

A study observes that neighborhoods with more parks have lower obesity rates. A city planner concludes that building more parks will reduce obesity. Which type of additional evidence would most strengthen the claim that parks reduce obesity?

Accepted Answer

A randomized experiment in which some neighborhoods are randomly assigned new parks

Answer

A larger observational study with more neighborhoods

Answer

A survey asking residents whether they use parks

Answer

A meta-analysis of observational studies about parks and health

Question 3

A researcher surveys 400 college students randomly selected from one university about social media use and GPA. The results show a negative association. Which statement correctly describes what the researcher can conclude?

Accepted Answer

There is a negative association between social media use and GPA among students at this university.

Answer

Heavy social media use causes lower GPA among all college students.

Answer

All students who reduce social media use will see GPA improvements.

Answer

The results apply to all college students because the sample was random.

Question 4

A clinical trial randomly assigns 500 patients to either a new drug or a placebo. The drug group shows significantly fewer symptoms. A doctor generalizes this to all patients with the condition. What concern is most valid?

Accepted Answer

The study can only be generalized to patients similar to those who participated in the trial.

Answer

The random assignment may have introduced bias.

Answer

Placebo effects make all clinical trials invalid.

Answer

A sample of 500 is too small to draw any conclusions.

Question 5

An education researcher randomly assigns 40 classrooms to use a new math curriculum and 40 to use the standard curriculum. At year-end, the new curriculum classrooms score significantly higher. What is the most valid conclusion?

Accepted Answer

The new curriculum causes higher math scores in classrooms like those in the study.

Answer

Every student who uses the new curriculum will score higher on math tests.

Answer

The new curriculum is superior to all other existing math curricula.

Answer

There is only a correlation between curriculum type and scores, not causation.

Question 6

A company surveys all of its 200 employees and finds that those who participate in the wellness program have fewer sick days. The CEO announces that the wellness program reduces sick days. What is the most significant flaw in this conclusion?

Accepted Answer

Employees who are already healthier may be more likely to join the program, creating selection bias.

Answer

The sample size of 200 is too small for any conclusions.

Answer

A census of all employees is less valid than a random sample.

Answer

The wellness program only covers physical health, not mental health.

Question 7

A study compares cancer rates in people who live near power lines versus those who do not, and finds a higher cancer rate near power lines. What is the most important limitation of this study?

Accepted Answer

The study is observational, so the higher cancer rate could be due to confounding variables rather than power line proximity.

Answer

The study did not measure the exact distance from power lines.

Answer

Cancer rates cannot be measured in observational studies.

Answer

The study should have used a larger sample to be valid.