AP Statistics Flashcards: Introduction to Experimental Design
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 36 cards to help you master important concepts.
Why is random assignment a critical element of a well-designed experiment?
Random assignment is used to create roughly equivalent groups by balancing out the effects of other variables among the treatment groups.
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Why is random assignment a critical element of a well-designed experiment?
Random assignment is used to create roughly equivalent groups by balancing out the effects of other variables among the treatment groups.
What is an explanatory variable?
An explanatory variable, also known as a factor, is the variable that is intentionally manipulated by the researchers in an experiment.
What is a confounding variable?
A confounding variable is a variable that is related to the explanatory variable and also influences the response variable.
In a well-designed experiment, what is the purpose of having similar units within each block?
Having similar units within each block helps to separate natural variability from the effects caused by the treatments.
To test a new teaching method, a researcher first separates students by their current grade (A, B, C) and then randomly assigns the new or old method to students within each grade group. What is this design?
This is a randomized complete block design, where grades are the blocks.
In the music genre experiment, the scientist measures the time it takes for participants to complete a puzzle. What is this measurement?
The time to complete the puzzle is the response variable.
In a clinical trial, the patients do not know if they are receiving the new medication or a sugar pill, but the doctors administering it do. What is this an example of?
This is a single-blind experiment.
A subject in a study reports feeling better after taking a pill, even though the pill contained no active medication. What is this an example of?
This is an example of the placebo effect.
In a double-blind experiment, who is unaware of the treatment assignments?
Neither the subjects nor the researchers who interact with the subjects know which treatment is being administered.
What is the placebo effect?
The placebo effect occurs when experimental units have a response to a placebo (a treatment with no active ingredient).
What is a control group?
A control group is a group of experimental units that receives no treatment or a placebo.
What is measured as the outcome in an experiment?
The response variable is the outcome measured after treatments have been administered.
What are treatments in an experiment?
Treatments are the different levels of an explanatory variable that are intentionally manipulated.
A matched pairs design is a special case of what other experimental design?
A matched pairs design is a special case of a block design.
What is another term for an explanatory variable?
Another term for an explanatory variable is a factor.
A scientist tests the effect of different music genres (classical, rock, silence) on task concentration. What is the music genre?
The music genre is the explanatory variable (or factor).
What is a response variable?
A response variable is the outcome that is measured after treatments have been administered to the experimental units.
What is a double-blind experiment?
In a double-blind experiment, neither the subjects nor the researchers interacting with them know which treatment is being received.
A study on a new weight-loss drug finds that participants taking the drug also reported an increase in exercise. If exercise also causes weight loss, what type of variable is it?
The increase in exercise is a confounding variable.
What is a completely randomized design?
In a completely randomized design, treatments are assigned to experimental units completely at random.
What are experimental units?
Experimental units are the individuals to which treatments are assigned in an experiment.
In a study on a new fertilizer, what are the individual plots of land that receive the treatments called?
The individual plots of land are the experimental units.
What is the relationship between a confounding variable, an explanatory variable, and a response variable?
A confounding variable is related to the explanatory variable and also influences the response variable, making it difficult to determine the treatment's true effect.
What is the primary purpose of blocking in an experiment?
Blocking ensures that experimental units within each block are similar, which helps to separate natural variability from the effects of the treatments.
What are some common methods for random assignment?
Methods for random assignment include using random number generators, random number tables, or drawing chips.
An experimenter uses a random number generator to assign 100 volunteers to either a treatment group or a control group. What type of experimental design is this?
This is a completely randomized design.
What is intentionally manipulated in an experiment?
The explanatory variable, or factor, is intentionally manipulated by the researcher.
What is a single-blind experiment?
In a single-blind experiment, either the subjects or the researchers interacting with them do not know which treatment is being received.
In the music genre experiment, what are 'classical', 'rock', and 'silence' specifically called?
These are the treatments, which are the levels of the explanatory variable.
What is a randomized complete block design?
In a randomized complete block design, experimental units are first grouped into blocks, and then treatments are assigned randomly within each block.
What is a matched pairs design?
A matched pairs design is a special case of a block design where subjects are arranged in pairs based on similar characteristics.
What is the purpose of using a control group?
A control group is used to provide a baseline for comparison to determine if the treatment of interest has an effect.
What is the key difference between a single-blind and a double-blind experiment?
In a single-blind experiment one group (subjects or researchers) is blinded, while in a double-blind experiment, both groups are blinded.
What are the four essential elements of a well-designed experiment?
A well-designed experiment includes comparison of treatments, random assignment, replication, and control of confounding variables.
A researcher wants to test the effect of a new golf ball on driving distance. Each golfer hits both the new and old ball in a random order. What type of design is this?
This is a matched pairs design, where each golfer acts as their own pair.
What are the three fundamental components of an experiment?
The components are the experimental units, the explanatory variable(s) being manipulated, and the response variable being measured.