AP Stats Stats: Evaluation Content and Structure 3 — Questions and Answers
Question 1: A researcher wants to ensure representation from each grade level in a school survey. Which method should they use?
- Simple random sample from the whole school
- Systematic sample from an enrollment list
- Stratified random sample by grade level (Correct answer)
- Voluntary response sample
Correct answer: Stratified random sample by grade level
Stratified sampling divides the population into subgroups and randomly samples from each, ensuring all strata are represented.
Question 2: An experiment uses a placebo control group. The primary purpose of the placebo is to:
- Reduce the cost of the experiment
- Allow researchers to remain blind to treatment assignments
- Control for the psychological effect of receiving a treatment (Correct answer)
- Increase the sample size of the study
Correct answer: Control for the psychological effect of receiving a treatment
A placebo controls for the psychological benefit subjects may experience simply from believing they are receiving treatment.
Question 3: Which principle of experimental design ensures that treatment groups are similar in all aspects other than the treatment itself?
- Replication
- Blocking
- Random assignment (Correct answer)
- Blinding
Correct answer: Random assignment
Random assignment distributes variation among groups so that, on average, groups differ only in the treatment applied.
Question 4: A study surveys only people who respond to an online invitation. This introduces which type of bias?
- Undercoverage bias
- Voluntary response bias (Correct answer)
- Leading question bias
- Nonsampling error
Correct answer: Voluntary response bias
Voluntary response bias occurs when participation is self-selected, typically over-representing people with strong opinions.
Question 5: In blocking, subjects are grouped by a characteristic before random assignment. What does blocking accomplish?
- It eliminates the need for a control group
- It reduces variation within treatment groups by controlling a known source of variability (Correct answer)
- It ensures the sample represents the population
- It prevents researchers from knowing treatment assignments
Correct answer: It reduces variation within treatment groups by controlling a known source of variability
Blocking groups similar subjects together and randomizes within blocks, reducing the impact of a known nuisance variable.
Question 6: When is it most appropriate to generalize the results of a study to a larger population?
- When the study used a large convenience sample
- When participants were randomly selected from the population of interest (Correct answer)
- When the study was double-blind
- When the experiment had a control group
Correct answer: When participants were randomly selected from the population of interest
Random selection from the population allows results to be generalized because the sample is representative.
Question 7: A survey about alcohol use is conducted face-to-face by police officers. Which bias is most likely?
- Undercoverage
- Non-response bias
- Response bias due to perceived social desirability (Correct answer)
- Voluntary response bias
Correct answer: Response bias due to perceived social desirability
Respondents are likely to underreport alcohol use to police officers to appear socially acceptable, causing response bias.
AP Stats Stats: Evaluation Content and Structure 3
A researcher wants to ensure representation from each grade level in a school survey.
Which method should they use?