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AP Statistics Practice Quiz: Selecting an Experimental Design

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 7 questions to check your progress.

Question 1 of 7

A researcher wants to test a new fertilizer on tomato plants in a greenhouse where plants on the west side receive more afternoon sun than plants on the east side. The researcher first groups the plants into an 'East' group and a 'West' group, and then randomly assigns the new fertilizer or a standard fertilizer to plants within each group. Why is this experimental design appropriate?

All Questions (7)

A researcher wants to test a new fertilizer on tomato plants in a greenhouse where plants on the west side receive more afternoon sun than plants on the east side. The researcher first groups the plants into an 'East' group and a 'West' group, and then randomly assigns the new fertilizer or a standard fertilizer to plants within each group. Why is this experimental design appropriate?

A) It ensures that the effect of sunlight is not confused with the effect of the fertilizer.

B) It simplifies the data analysis by creating fewer treatment groups.

C) It increases the total number of plants that can be used in the experiment.

D) It is the only design that allows for the use of a standard fertilizer as a control.

Correct Answer: A

This design (a randomized block design) is appropriate because it controls for a known confounding variable: the amount of sunlight. By separating the plants into blocks based on location ('East' and 'West'), the researcher can isolate the variability due to sunlight from the variability due to the fertilizer, leading to a more accurate conclusion about the fertilizer's effectiveness.

A small startup with a limited budget wants to conduct an experiment to see if their new app interface is more user-friendly than their old one. Which of the following describes the most important consideration when selecting their experimental design?

A) The design must be complex enough to account for every possible user characteristic.

B) The design must be chosen to maximize statistical power, regardless of the cost or time involved.

C) The design must be feasible to implement given the significant constraints on company resources.

D) The design must be identical to one used by a major competitor to ensure comparability.

Correct Answer: C

The provided content states that each experimental design has advantages and disadvantages depending on resources. For a company with a limited budget, the primary consideration is feasibility. A complex, expensive, or time-consuming design would be inappropriate, even if it were statistically powerful. The chosen design must be practical within their resource constraints.

To test the effectiveness of a new skin cream, researchers measure the skin condition of 50 participants. They then have each participant use the cream for 30 days and measure their skin condition again. Why is this 'before-and-after' design particularly appropriate for this research question?

A) It is less expensive than a design that uses a separate control group.

B) It controls for the natural variability in skin condition that exists between different people.

C) It guarantees that the skin cream will show a positive effect.

D) It allows researchers to use a larger sample size than other designs.

Correct Answer: B

This design (a matched pairs design) is appropriate because each participant serves as their own control. This design effectively controls for confounding variables related to individual differences, such as genetics, diet, and lifestyle, which could otherwise affect the outcome. By comparing each person to themselves, the design can more precisely measure the effect of the cream.

A study on a new teaching method for reading randomly assigns 200 first-grade students to either the new method or the standard method. What is a potential disadvantage of this completely randomized design?

A) It cannot establish a cause-and-effect relationship between the teaching method and reading ability.

B) By pure chance, one group might end up with a higher concentration of students with a pre-existing aptitude for reading.

C) This design is significantly more difficult and resource-intensive to implement than other designs.

D) The results from the study cannot be generalized to a larger population of students.

Correct Answer: B

A key disadvantage of a completely randomized design is that it relies entirely on chance to create balanced groups. It is possible that, by random chance, one group could end up with a disproportionate number of students who are already strong readers or have more parental support at home. This would confound the results, making it difficult to determine if the outcome was due to the teaching method or the pre-existing imbalance.

When planning an experiment, a researcher identifies a variable that is not of primary interest but is known to affect the response variable. The researcher decides to create groups, or blocks, based on this variable and then run the experiment separately within each block. What is the primary advantage of choosing this design?

A) It allows the researcher to completely ignore the effects of the blocking variable in the final analysis.

B) It reduces the amount of data that needs to be collected.

C) It provides a more precise estimate of the treatment effect by accounting for the variability caused by the blocking variable.

D) It ensures that the results of the experiment will be statistically significant.

Correct Answer: C

The main advantage of a block design is that it isolates and accounts for the variability in the response that is caused by the blocking variable. By controlling for this source of variation, the design reduces the overall 'noise' in the data, making it easier to detect the true effect of the treatment being studied. This leads to a more powerful and precise conclusion.

An agricultural scientist is designing an experiment to test three new pesticides on crop yield. To control for known sources of variation, she decides to block by soil type, irrigation method, and sun exposure. What is a likely disadvantage of this highly complex experimental design?

A) The design eliminates the need for random assignment of the pesticides within the blocks.

B) The results will be less precise than if a completely randomized design were used.

C) It may be logistically difficult to find enough plots of land that fit into each specific combination of blocking factors.

D) The design makes it impossible to determine which of the three pesticides is most effective.

Correct Answer: C

While blocking on multiple variables can theoretically increase precision, a significant practical disadvantage is the logistical complexity. As the number of blocking variables increases, the number of unique blocks (e.g., 'sandy soil with drip irrigation and full sun') multiplies. It can become very difficult and costly to find enough experimental units for every single block, potentially making the experiment infeasible.

According to the principles of experimental design, what is the most fundamental factor that should guide a researcher's choice of a particular design?

A) The statistical software available for data analysis.

B) The specific research question the experiment aims to answer.

C) The number of researchers on the project team.

D) The desire to publish the results in a prestigious journal.

Correct Answer: B

The primary goal of any experiment is to answer a research question. Therefore, the most appropriate experimental design is the one that is best suited to provide a clear and valid answer to that specific question. All other factors, such as resources, staffing, and analysis tools, are secondary considerations that relate to the feasibility of implementing the ideal design.