Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 3

Question 1

A researcher randomly selects 1,000 adults from across the United States and finds that adults who sleep 8 hours per night report higher life satisfaction. Which statement is best supported by this study?

Accepted Answer

There is an association between sleeping 8 hours and higher life satisfaction that is likely representative of U.S. adults.

Answer

The random sample supports generalization to U.S. adults, but because this is observational (no random assignment), only an association — not causation — can be concluded.

Question 2

A study randomly assigns participants to two diet groups for 12 weeks: a high-protein diet or a standard diet. The high-protein group loses significantly more weight. Which conclusion is best supported?

Accepted Answer

A high-protein diet causes more weight loss among people similar to study participants.

Answer

Random assignment allows a causal conclusion; however, the result only generalizes to populations similar to the study participants.

Question 3

An observational study follows 5,000 people over 20 years and finds that those who regularly volunteer have longer lifespans. What is the most important limitation of this finding?

Accepted Answer

Since participants were not randomly assigned to volunteer or not, the association could be due to confounding variables such as overall health or social status.

Answer

Without random assignment, people who volunteer may differ systematically (e.g., better health, higher income) from those who don't, making it impossible to attribute longer life to volunteering.

Question 4

A school randomly selects 80 students to participate in a new after-school reading program and observes that they read better at year-end than a comparison group. Which aspect of the study design limits the strength of a causal conclusion?

Accepted Answer

The students were randomly selected but not randomly assigned to treatment and control groups.

Answer

Random selection determines who is in the study (generalizability), but random assignment is needed to form comparable treatment and control groups; without it, the causal link is uncertain.

Question 5

A poll randomly samples 2,000 U.S. adults and finds that 65% support stricter environmental regulations. Based on this, which conclusion is valid?

Accepted Answer

Approximately 65% of U.S. adults support stricter environmental regulations.

Answer

A large random sample of U.S. adults supports a generalization about the population; however, this is descriptive — no causal claims about causes of political preferences can be drawn.

Bluebook SAT Practice Test

Bluebook SAT Practice Test

Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 3