AP Statistics Practice Quiz: Introduction to 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 16 questions to check your progress.

Question 1 of 16

In an experiment, what are the individuals to which treatments are assigned called?

A)Explanatory variablesB)Response variablesC)Experimental unitsD)Confounding variables

All Questions (16)

In an experiment, what are the individuals to which treatments are assigned called?

A) Explanatory variables

B) Response variables

C) Experimental units

D) Confounding variables

Correct Answer: C

According to the provided content, 'Experimental units are the individuals to which treatments are assigned.' The other options are different components of an experiment.

A researcher wants to test the effect of a new fertilizer on tomato plant yield. The amount of fertilizer applied (none, 10g, 20g) is which component of the experiment?

A) The response variable

B) The explanatory variable

C) The experimental units

D) A confounding variable

Correct Answer: B

The fertilizer is the variable being intentionally manipulated by the researcher to see its effect on the outcome. The content states that an 'explanatory variable (factor) is intentionally manipulated.'

Which of the following is NOT listed as a required element of a well-designed experiment?

A) Random assignment

B) Replication

C) Double-blinding

D) Control of confounding variables

Correct Answer: C

The content states that 'A well-designed experiment includes comparison of treatments, random assignment, replication, and control of confounding variables.' While double-blinding is a useful technique, it is not listed as a core required element for all well-designed experiments.

An experiment is conducted to see if a new medication reduces blood pressure. One group receives the new medication, and another group receives a sugar pill. The group receiving the sugar pill is known as what?

A) The treatment group

B) The blocked group

C) The confounding group

D) The control group

Correct Answer: D

The content defines a control group as one that 'receives no treatment or a placebo to determine if the treatment of interest has an effect.' The sugar pill is a placebo.

A researcher is studying the effect of two different teaching methods on test scores. They are concerned that students' prior academic performance might affect the results. To account for this, they first group students by high, medium, and low GPA, and then randomly assign the teaching methods within each group. What type of design is this?

A) Completely randomized design

B) Single-blind experiment

C) Randomized complete block design

D) Matched pairs design

Correct Answer: C

The students are grouped into blocks (high, medium, low GPA) based on a similar characteristic. The content states that in a 'randomized complete block design, treatments are assigned randomly within each block' to ensure units within each block are similar.

In an experiment testing a new allergy medication, the participants do not know if they are receiving the medication or a placebo, but the doctors administering it do. This is an example of what?

A) A double-blind experiment

B) A single-blind experiment

C) A matched pairs design

D) A completely randomized design

Correct Answer: B

The content defines a single-blind experiment as one where 'either the subjects or the researchers do not know which treatment is being received.' In this case, the subjects are unaware.

What is the term for the different levels of an explanatory variable that are applied in an experiment?

A) Outcomes

B) Treatments

C) Blocks

D) Units

Correct Answer: B

The content explicitly states that the levels of an explanatory variable 'are called treatments.'

A variable that is related to the explanatory variable and also influences the response variable, making it difficult to determine the true effect of the treatment, is called a:

A) Placebo

B) Factor

C) Confounding variable

D) Response variable

Correct Answer: C

This is the definition of a confounding variable, which is 'related to the explanatory variable and influences the response variable.'

What is the primary purpose of using a blocking design in an experiment?

A) To eliminate the placebo effect by grouping similar subjects.

B) To ensure that neither the subjects nor the researchers know which treatment is being received.

C) To separate natural variability from the effects of the treatments by creating homogeneous groups.

D) To assign treatments to experimental units completely at random without any grouping.

Correct Answer: C

The content states that blocking 'helps to separate natural variability from treatment effects' by ensuring units within each block are similar. This allows for a more precise comparison of the treatments.

In a study on the effectiveness of a new energy drink, researchers measure the change in participants' heart rates after consumption. What is the response variable in this study?

A) The new energy drink

B) The participants

C) The change in heart rate

D) The placebo drink

Correct Answer: C

The response variable is the outcome being measured. In this case, the researchers are measuring the 'change in heart rate' after the treatment has been administered.

An experiment is designed to test the durability of two types of car tires. To control for the variability between different cars and driving habits, each car is fitted with one tire of each type. The position of the tires (e.g., front-left, rear-right) is randomized for each car. This experimental design is best described as:

A) A completely randomized design

B) A double-blind experiment

C) A randomized complete block design

D) A matched pairs design

Correct Answer: D

The content states that a matched pairs design is a special case of a block design where subjects are arranged in pairs. Here, each car acts as a 'pair' or block of two, receiving both treatments (tire types).

The phenomenon where participants in an experiment show a response to an inert treatment is known as:

A) The blinding effect

B) The confounding effect

C) The replication effect

D) The placebo effect

Correct Answer: D

The content defines the placebo effect as occurring 'when experimental units have a response to a placebo.' A placebo is an inert treatment.

Which of the following describes a double-blind experiment?

A) Treatments are assigned to experimental units completely at random.

B) Only the researchers know which treatment each subject is receiving.

C) Neither the subjects nor the researchers interacting with them know which treatment is being administered.

D) Subjects are arranged in pairs based on similar characteristics.

Correct Answer: C

This is the definition provided in the content: 'In a double-blind experiment, neither the subjects nor the interacting researchers know which treatment is being received.'

In which experimental design are treatments assigned to experimental units without any form of grouping or pairing?

A) Matched pairs design

B) Randomized complete block design

C) Completely randomized design

D) Double-blind design

Correct Answer: C

The content specifies that 'In a completely randomized design, treatments are assigned to experimental units completely at random,' which implies the absence of pre-assignment grouping like blocking or pairing.

Which of the following is a valid method for performing random assignment in an experiment?

A) Allowing subjects to choose their own treatment group.

B) Assigning the first 20 subjects to one group and the next 20 to another.

C) Using a random number generator to assign subjects to groups.

D) Assigning subjects based on their last names.

Correct Answer: C

The content lists 'random number generators, tables, or drawing chips' as acceptable methods for random assignment. The other options introduce bias and are not random.

A study investigates whether listening to classical music or pop music helps students focus while studying. 100 students are recruited. The researchers use a coin flip for each student to determine whether they will be in the classical music group or the pop music group. After a 30-minute study session, students take a short comprehension test. In this experiment, what are the treatments?

A) The 100 students.

B) The comprehension test scores.

C) Classical music and pop music.

D) The coin flip.

Correct Answer: C

The treatments are the different levels of the explanatory variable (type of music) that are being compared. The content states that the levels of an explanatory variable are called treatments.