Bluebook SAT Test Evaluating Statistical Claims: Observational Studies and Experiments 8

Question 1

A study randomly assigns 300 adults to participate in a strength training program or a stretching-only program.
After 12 weeks, the strength training group shows greater bone density.
The researcher concludes strength training causes increased bone density.
Which additional question is most important for evaluating this conclusion?

Accepted Answer

Are the study participants representative of the broader adult population of interest?

Answer

Was the study conducted in a gym or a laboratory?

Answer

Was the stretching program the same duration as strength training?

Answer

Were the participants told which group they were in?

Question 2

A poll of 1,200 randomly selected U.S. voters finds that 54% favor a specific immigration policy. Which conclusion is best supported?

Accepted Answer

A majority of U.S. voters likely favor this policy, subject to a margin of error.

Answer

Exactly 54% of all U.S. voters favor this policy.

Answer

The policy will pass because more than half favor it.

Answer

Immigration policy preferences cause certain voting behaviors.

Question 3

A researcher notices that ice cream sales and drowning rates are highly correlated throughout the year. She concludes that ice cream causes drowning. What is the most likely explanation for this correlation?

Accepted Answer

A confounding variable — hot weather — increases both ice cream sales and swimming (and therefore drowning).

Answer

People who eat ice cream are more likely to swim unsafely.

Answer

The data was collected incorrectly, inflating the correlation.

Answer

Drowning rates cause ice cream sales to increase.

Question 4

A randomized clinical trial shows that Drug X reduces migraines better than a placebo in a diverse national sample of 2,000 adults. A neurologist concludes that Drug X should be the first-line treatment for all adults with migraines. Which statement about this conclusion is correct?

Accepted Answer

The conclusion is reasonable but should be further evaluated against side effects, cost, and results in subgroups.

Answer

The conclusion is fully supported; large randomized trials prove universal effectiveness.

Answer

The conclusion is invalid because randomized trials only work for acute conditions.

Answer

The conclusion requires replication in observational studies before being accepted.

Question 5

A high school conducts an experiment where 10 volunteering teachers adopt a new grading method and their students are compared to students of non-participating teachers. Students in the new grading method classes earn higher grades. What is the most significant flaw?

Accepted Answer

Teachers who volunteered may be more skilled or motivated, confounding the relationship between grading method and grades.

Answer

The sample of 10 teachers is too small for meaningful analysis.

Answer

The experiment should have measured standardized test scores instead of grades.

Answer

The non-participating teachers were not randomly selected as a control group.

Question 6

Based on an observational study, a health organization claims that people who eat more vegetables have fewer depressive episodes. Which of the following, if true, would most weaken a causal interpretation?

Accepted Answer

People with lower depression are more likely to have energy and motivation to prepare and eat healthy meals.

Answer

The study included over 10,000 participants.

Answer

The study measured vegetable intake through self-reporting.

Answer

The study controlled for age and gender.

Question 7

A study randomly selects 400 schools nationwide and observes that schools with larger libraries have higher reading proficiency. A policy advisor concludes that expanding libraries will improve reading proficiency. What is the best evaluation of this recommendation?

Accepted Answer

The recommendation is premature because the observational study cannot establish that larger libraries cause higher proficiency.

Answer

The recommendation is justified because the study used a nationally representative random sample.

Answer

The recommendation is justified because library size directly measures reading opportunity.

Answer

The recommendation requires only a larger sample size to be valid.