Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 5

Question 1

A study randomly assigns 200 participants to either a sleep restriction group (6 hours/night) or a normal sleep group (8 hours/night) for 2 weeks. The restricted sleep group performs worse on memory tests. What is the most valid conclusion?

Accepted Answer

For people similar to those in this study, sleep restriction likely causes worse memory performance.

Answer

Random assignment supports a causal conclusion; however, generalizability is limited to populations similar to the study participants.

Question 2

A researcher observes that counties with higher rates of library visits also have higher graduation rates. She claims that library use causes higher graduation rates. What is wrong with her reasoning?

Accepted Answer

The association might be explained by a confounding variable, such as overall community investment in education.

Answer

Counties with more libraries likely invest more in education overall, making community investment a confounding variable that could explain both library visits and graduation rates.

Question 3

Participants in a study are randomly selected from 10 different cities and randomly assigned to either an intervention or control group. The intervention group shows a significant positive outcome. To which population can results be most validly generalized?

Accepted Answer

People in cities similar to the 10 cities studied

Answer

Random selection from 10 cities supports generalization to populations in similar cities; random assignment supports causal inference but does not expand the scope of generalizability.

Question 4

A study of 10,000 adults finds that vegetarians have lower rates of type 2 diabetes than non-vegetarians. A nutritionist claims this proves vegetarian diets prevent diabetes. What is the most valid critique?

Accepted Answer

Vegetarians may differ from non-vegetarians in other healthy behaviors (exercise, lower smoking) that reduce diabetes risk, making causation unclear.

Answer

Confounding lifestyle factors (e.g., exercise, smoking, stress management) common among vegetarians could explain the lower diabetes rate, undermining a causal claim.

Question 5

A randomized experiment gives one group a mindfulness app and the other no app, then measures anxiety. The app group reports lower anxiety. Which of the following would most limit generalizing this result to all adults?

Accepted Answer

Participants volunteered for the study, so they may not represent all adults.

Answer

Volunteers may be more motivated or open to technology than the general adult population, limiting how well the results generalize beyond similar volunteers.

Bluebook SAT Practice Test

Bluebook SAT Practice Test

Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 5