Worked examplesThree real introduction to experimental design questions
From the practice pool, not the mock papers — each with the reasoning that produces the answer.
100% of them come with a figure. Reading the graph or diagram correctly is most of the work here before any content knowledge applies.
92% test a single AP skill: Statistical Argumentation. That makes this topic unusually predictable to prepare for.
Statistical Argumentation · with figure
For the mobile dental clinic alpha cycle, researchers randomly assign comparable patients to receive either a new reminder card reminder or the usual reminder, then compare appointment follow-up. What feature supports a cause-and-effect conclusion?
- AA large voluntary response survey about appointment follow-up.
- BRandom assignment of patients to reminder conditions.correct
- CReporting only the group with the better appointment follow-up.
- DUse volunteers.
- EUsing only one neighborhood to make data collection easier.
Why B is correct
Random assignment to the reminder treatments helps balance other variables between groups, so differences in appointment follow-up can more plausibly be attributed to the reminder condition.
Random assignment in an experiment for mobile dental clinic alpha cycle: the important cue is the mobile dental clinic alpha cycle setting. Match the method to the way the data are collected or the statistic is computed, then state the conclusion in the language of the stem.
Statistical Argumentation · with figure
A food pantry route alpha cycle test gives one group a realistic-looking inactive cooler label and keeps evaluators unaware of group labels while measuring pickup wait time. Which design feature is described?
- AA placebo with evaluator blinding to reduce expectation effects.correct
- BA residual plot for a regression line.
- CA large convenience sample removes selection bias because increasing sample size alone makes the sample representative.
- DA census of all possible households.
- EUndercoverage from excluding a route zone.
Why A is correct
The inactive but realistic-looking cooler label is a placebo, and keeping evaluators unaware of group labels is blinding, both of which reduce expectation effects when measuring pickup wait time.
Placebo and blinding in food pantry route alpha cycle: the important cue is the food pantry route alpha cycle setting. Match the method to the way the data are collected or the statistic is computed, then state the conclusion in the language of the stem.
Statistical Argumentation · with figure
For the campus garden alpha cycle, researchers randomly assign comparable students to receive either a new bin sticker reminder or the usual reminder, then compare compost bin use. What feature supports a cause-and-effect conclusion?
- AReporting only the group with the better compost bin use.
- BUse volunteers.
- CUsing only one residence hall to make data collection easier.
- DRandom assignment of students to reminder conditions.correct
- EA large voluntary response survey about compost bin use.
Why D is correct
Random assignment to the reminder treatments helps balance other variables between groups, so differences in compost bin use can more plausibly be attributed to the reminder condition.
Random assignment in an experiment for campus garden alpha cycle: the important cue is the campus garden alpha cycle setting. Match the method to the way the data are collected or the statistic is computed, then state the conclusion in the language of the stem.
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Last reviewed 2026-08-28. Topic and unit names follow the
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