AP Statistics
AP Stats Unit 1 Part 2 (1F 1H) Super Hard MCQ
Shared by ashtont · Oct 7, 2026 · 7 plays
51 questions across 3 sections. After every answer you’ll see why each choice is right or wrong, not just the one you picked.
Sample questions
Open a question to see the answer choices and the correct answer.
Sixty adults who answered a newspaper ad are randomly assigned to take a new sleep supplement or a placebo for a month. The supplement group falls asleep significantly faster. What conclusion is appropriate?
- A. The supplement caused faster sleep onset, for all adults
- B. The supplement is associated with faster sleep onset for all adults, but causation cannot be concluded
- C. No conclusion is possible, because the subjects were volunteers
- D. The supplement caused faster sleep onset, for adults similar to those who volunteered ✓
Correct answer: D. Random assignment supports cause and effect. The subjects were volunteers, not a random sample, so results generalize only to people similar to them.
A random sample of 900 registered voters in a city is surveyed. Those who drink coffee daily report less sleep, on average, than those who do not. What conclusion is appropriate?
- A. Among the city's registered voters, daily coffee drinking is associated with less sleep, but the study cannot show that coffee is the cause. ✓
- B. Coffee causes the city's registered voters to sleep less.
- C. Among the 900 people surveyed, coffee is associated with less sleep, but nothing can be said about other voters.
- D. Among all adults in the city, daily coffee drinking is associated with less sleep.
Correct answer: A. Random selection allows generalizing to the population sampled from. No treatment was assigned, so confounding variables such as work schedule could explain the difference.
In 2024, researchers select 2,000 nurses and use employment records from 2010 to 2023 to find how many years each worked night shifts. They then compare current blood pressure for those with long and short night-shift histories. What type of study is this?
- A. A prospective observational study
- B. An experiment, with night-shift history as the treatment
- C. A retrospective observational study ✓
- D. A census of nurses
Correct answer: C. No treatment was imposed, and the nurses were selected at one point in time with data gathered from the past.
An observational study finds that high school students who eat breakfast every day have higher GPAs than students who do not. Which variable is a confounding variable?
- A. Hours of studying per week, if it raises GPA but is unrelated to whether a student eats breakfast
- B. Household income, if students from higher-income homes are both more likely to eat breakfast and more likely to have higher GPAs ✓
- C. Whether a student's school serves breakfast, if it affects breakfast eating but is unrelated to GPA
- D. GPA, because it differs between the two groups
Correct answer: B. A confounding variable must be associated with both the explanatory variable (breakfast) and the response (GPA), so it offers another explanation for the relationship.
Researchers will randomly assign adult volunteers who have insomnia to take a new supplement or a placebo and will record how long each takes to fall asleep. Which investigative question best fits this study?
- A. Does the supplement lower the mean time to fall asleep for all adults?
- B. For adults with insomnia like those who volunteered, does taking the supplement cause a lower mean time to fall asleep than taking a placebo? ✓
- C. Is taking the supplement associated with the time it takes volunteers to fall asleep?
- D. How well do adults with insomnia sleep?
Correct answer: B. It names the variable, the parameter and direction (a lower mean time), the group the results can apply to (people like the volunteers) and the kind of conclusion random assignment allows (cause and effect).