Psychology Quiz: Experimental Design

20 questions · exam conditions

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Experimental DesignQuestion 1 of 20

A researcher wants to conduct an experiment to test the hypothesis that 'stress impairs memory.' Which of the following designs provides the best operationalization of the independent and dependent variables for this purpose?

Surveying college students about their stress levels during finals week and their self-perceived memory quality.

Having participants watch a stressful film or a neutral film, and then measuring their physiological arousal via heart rate.

Comparing the memory performance of a group of participants with a diagnosed anxiety disorder to a group without a diagnosis.

Randomly assigning participants to either submerge their hand in ice water (a stressor) or lukewarm water, and then having them recall a list of words.

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Psychology Quiz

Psychology Quiz: Experimental Design

Practice Experimental Design in Psychology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Experimental Design, giving you a quick way to practice the rules, question types, and explanations that matter most for Psychology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Surveying college students about their stress levels during finals week and their self-perceived memory quality.
Having participants watch a stressful film or a neutral film, and then measuring their physiological arousal via heart rate.
Comparing the memory performance of a group of participants with a diagnosed anxiety disorder to a group without a diagnosis.
Randomly assigning participants to either submerge their hand in ice water (a stressor) or lukewarm water, and then having them recall a list of words. (correct answer)

Explanation: A good experiment must manipulate the IV (stress) and measure the DV (memory). 'D' does this effectively: it manipulates stress using a standardized procedure (cold pressor test) and measures memory with a recall task. 'A' is a correlational design, not an experiment. 'B' operationalizes stress but fails to measure the correct dependent variable (memory); it measures arousal instead. 'C' is a quasi-experimental design because it uses pre-existing groups rather than manipulating stress directly, so other factors associated with anxiety disorders could be confounds.

Question 2

A researcher hypothesizes that exposure to nature improves mood. On a sunny day, she has a group of participants sit in a park for 20 minutes. On a rainy day, she has a different group of participants sit in a windowless room for 20 minutes. After the intervention, she measures their mood and finds the park group's mood is significantly better.

The most significant flaw that prevents a valid causal conclusion in this study is the:

use of a subjective self-report measure for the dependent variable (mood).
absence of a pretest to measure participants' baseline mood before the intervention.
confounding of the independent variable (location) with the weather conditions. (correct answer)
lack of a true no-intervention control group.

Explanation: A confounding variable is an extraneous variable that varies systematically along with the independent variable, providing an alternative explanation for the results. In this case, location (park vs. room) is perfectly confounded with weather (sunny vs. rainy). It is impossible to know if the better mood was caused by being in nature or by the pleasant sunny weather. 'A' is not a flaw; self-report is a standard way to measure mood. 'B' is a weakness, but less critical than the confound. 'D' is incorrect as the windowless room group serves as a comparison/control condition, albeit a flawed one.

Question 3

A researcher manipulates a variable of interest and includes a comparison group, but does not use random assignment to place participants in the groups. Which statement most accurately describes this study?

It is a quasi-experiment whose ability to support a causal claim is weakened. (correct answer)
It is a true experiment because it involves the manipulation of an independent variable.
It is a correlational study because causation cannot be inferred.
It has high internal validity but may have low external validity.

Explanation: When you encounter questions about research design, focus on the three key elements that distinguish experimental approaches: manipulation of variables, comparison groups, and random assignment. Each element affects what conclusions you can draw from the study. This study has two of the three experimental elements—variable manipulation and a comparison group—but lacks random assignment. This makes it a quasi-experiment. Random assignment is crucial because it helps ensure that groups are equivalent at the start, reducing the chance that pre-existing differences between participants (rather than your manipulation) explain any observed effects. Without it, your ability to make strong causal claims is compromised, though not eliminated entirely. Choice A correctly identifies this as a quasi-experiment with weakened causal inference. The study can still provide valuable evidence, but you must be more cautious about claiming causation. Choice B is wrong because true experiments require all three elements, including random assignment. Variable manipulation alone isn't sufficient. Choice C incorrectly labels this as correlational. Correlational studies don't involve manipulation—they just measure existing relationships between variables. Since this study manipulates a variable, it's experimental in nature, just not a true experiment. Choice D reverses the validity issue. This design actually has potentially low internal validity (ability to infer causation) due to the lack of random assignment, though external validity could vary depending on other design features. Remember: quasi-experiments fall between correlational and true experimental designs. They're stronger than correlational studies but weaker than true experiments for establishing causation.

Question 4

A researcher studies the effects of caffeine on problem-solving. Participants are randomly assigned to drink a cup of coffee. Group A receives regular caffeinated coffee. Group B receives decaffeinated coffee that has been specially prepared to taste, smell, and look identical to the regular coffee. Participants are not told which type they received.

The use of identical-tasting decaffeinated coffee for Group B is a critical part of this design because it serves as a:

manipulation check to ensure the independent variable was administered correctly.
placebo control to account for the effects of participant expectations. (correct answer)
standardization procedure to reduce random error in the experiment.
method for ensuring that the two groups are equivalent on caffeine tolerance.

Explanation: The goal is to isolate the chemical effects of caffeine. By giving the control group a beverage that is identical in every way except for the active ingredient (caffeine), the researcher controls for the psychological effects of simply being in an experiment and consuming what one believes is coffee. This is a placebo control. Any difference between the groups can then be more confidently attributed to the caffeine itself, rather than to participant expectations. 'A' refers to checking if the IV manipulation worked. 'C' is too general. 'D' is a participant characteristic that is controlled by random assignment.

Question 5

A researcher wants to know if people rate jokes as funnier when in a group versus when alone. They have each participant rate a series of 10 jokes while alone in a room. A week later, the same participants return and rate 10 different but equivalent jokes while in a room with two other people.

A primary methodological challenge specific to this within-subjects design is:

ensuring the initial equivalence of the 'alone' and 'group' conditions, since individual differences in humor appreciation could be a confound.
the potential for order effects, such as practice or fatigue, to influence the ratings in the second condition. (correct answer)
the difficulty of recruiting a large enough sample to have sufficient statistical power.
the ethical implications of having participants rate jokes without knowing the study's true purpose.

Explanation: This is a within-subjects (or repeated measures) design because the same participants are in both conditions. A key disadvantage of this design is the potential for order effects: the experience of being in the first condition can influence performance in the second. For example, participants might be bored by the second session (fatigue effect) or get better at the rating task (practice effect). 'A' is incorrect because a major strength of this design is that it eliminates concerns about initial group equivalence on individual differences. 'C' and 'D' are general research challenges not specific to this design type.

Question 6

A researcher studies the effect of a new mindfulness app on student test anxiety. Group A is instructed to use the app for 15 minutes daily. Group B is instructed to sit quietly with their eyes closed for 15 minutes daily. Group C is given no special instructions regarding daily activities. The researcher measures anxiety using a standardized questionnaire immediately before a major exam and also tracks participants' self-reported daily screen time.

In this study, which of the following is the independent variable?

The score on the standardized anxiety questionnaire.
The amount of daily screen time reported by participants.
The specific 15-minute daily activity participants were assigned. (correct answer)
The use versus non-use of the mindfulness app.

Explanation: The independent variable (IV) is the factor that the researcher manipulates to observe its effect. In this experiment, the researcher is systematically varying the type of daily activity across three levels: mindfulness app, quiet sitting, and no instructions. Therefore, the assigned activity is the IV. 'A' is the dependent variable (the outcome being measured). 'B' is an extraneous variable being tracked. 'D' is an incomplete description of the IV, as it ignores the second, active control group (quiet sitting) and reduces the three-level variable to a two-level comparison.

Question 7

A cognitive psychologist wants to test if a new mnemonic technique improves memory for lists of words. She randomly assigns 100 undergraduates to either a group that learns the new technique or a group that uses their own typical study methods. The primary purpose of randomly assigning participants is to:

ensure that the sample of 100 undergraduates is representative of the general population.
increase the likelihood that pre-existing differences in memory ability are balanced between the two groups. (correct answer)
control for situational confounding variables, such as the time of day the experiment is run.
prevent participants' expectations about the new technique from influencing the results.

Explanation: Random assignment is a core feature of experimental design used to increase internal validity. Its purpose is to create groups that are approximately equivalent at the start of the study by distributing individual differences (like baseline memory ability, motivation, intelligence) between the groups by chance. 'A' describes the purpose of random sampling, which affects external validity (generalizability). 'C' refers to situational variables that must be controlled through standardization of procedures. 'D' relates to controlling for expectancy effects, which is typically addressed with blinding and placebo controls.

Question 8

A school district implements a new, expensive "growth mindset" curriculum in all its high-poverty schools. In its low-poverty schools, it continues with the standard curriculum. At the end of the year, students in the high-poverty schools show greater gains in math scores than students in the low-poverty schools. The district concludes the new curriculum caused the improvement.

Why is the district's causal conclusion not well-supported by this research design?

The study lacks a control group because all schools received some form of curriculum.
The dependent variable, math score gains, is not an objective measure of learning.
The study only shows a correlation, and correlation does not equal causation.
Pre-existing systemic differences between high-poverty and low-poverty schools were not controlled for. (correct answer)

Explanation: This is a quasi-experimental design because the groups (high- vs. low-poverty schools) were not created through random assignment. Therefore, there could be many systematic differences between them other than the curriculum (e.g., teacher resources, parental involvement, student health) that could explain the difference in outcomes. This is a major confound. 'A' is incorrect; the standard curriculum schools serve as a comparison group. 'B' is a potential measurement issue but not the core design flaw. 'C' is a true but imprecise statement; 'D' provides the specific reason why the study is only correlational and cannot support a causal claim.

Question 9

Researchers investigate whether ambient noise affects creative problem-solving. Participants are randomly assigned to a lab under one of three conditions: silence, low-level white noise, or high-level white noise. They are then given 10 minutes to solve a series of insight puzzles. To ensure the randomization worked, all participants first complete a standardized IQ test upon arrival.

In this experiment, what is the role of the IQ test?

It is a second independent variable being manipulated by the researchers.
It is the primary dependent variable used to measure creativity.
It is a potential confounding variable that was unintentionally introduced.
It is a measured variable used to check the initial equivalence of the randomly assigned groups. (correct answer)

Explanation: The IQ test is not being manipulated (so it's not an IV) and it's not the outcome of interest (so it's not the DV). Instead, it is measured to verify that random assignment was successful in creating groups that are, on average, equivalent in terms of general cognitive ability. If one group happened to have a significantly higher average IQ by chance, it could compromise the study's internal validity. Measuring it allows the researchers to confirm this is not the case or statistically control for it if necessary.

Question 10

A research article abstract states, "Our results demonstrate that a daily 30-minute session of aerobic exercise causes a significant reduction in symptoms of depression."

Based on this specific causal claim, the study most likely employed which research method?

A longitudinal study tracking the exercise habits and depression levels of a large cohort over 10 years.
An experiment where participants were randomly assigned to an exercise condition or a no-exercise control condition. (correct answer)
A correlational study finding a strong negative association between time spent exercising and depression scores.
A series of in-depth case studies of individuals who successfully used exercise to manage their depression.

Explanation: The word "causes" implies a causal relationship. To establish causation, a researcher must conduct a true experiment, which involves manipulating the independent variable (exercise) and using random assignment to control for pre-existing differences. Correlational, longitudinal, and case study methods can identify relationships and generate hypotheses, but they cannot, on their own, establish cause and effect due to the third-variable problem and/or the directionality problem.

Question 11

A social psychologist studies how mood and audience size affect confidence in public speaking. Participants are first shown either a comedy clip (positive mood induction) or a sad drama clip (negative mood induction). They are then randomly assigned to give a 3-minute speech to either one person or a group of ten people. After the speech, they rate their own confidence on a 1-10 scale.

What is the dependent variable in this experiment?

The type of video clip shown (comedy or drama).
The number of people in the audience (one or ten).
The participant's self-rated confidence score. (correct answer)
The interaction between the participant's mood and the audience size.

Explanation: The dependent variable (DV) is the outcome that the researcher measures to see if it is affected by the independent variables. In this case, the researcher is measuring the participants' confidence ratings. 'A' and 'B' are the two independent variables that are being manipulated by the researcher. 'D' is a potential result or finding of the study (i.e., whether the effect of one IV depends on the level of the other IV), but it is not the variable being directly measured from each participant.

Question 12

An educational psychologist tests a new math tutoring method. She randomly assigns students with either high or low prior math achievement to receive either the new tutoring method or the standard method. She finds that the new method is highly effective for students with low prior achievement, but is no different from the standard method for students with high prior achievement.

This outcome indicates that the causal effect of the tutoring method on student learning:

is dependent on the students' level of prior math achievement. (correct answer)
is less important than the main effect of prior achievement.
is confounded by the students' prior math achievement.
is positive overall because it improved scores for some students.

Explanation: When you encounter experimental design questions in psychology, focus on identifying the relationship between variables and whether effects depend on other factors. This study uses a factorial design that can reveal interactions between variables. The key finding here is that the tutoring method's effectiveness varies based on students' prior achievement level - it helps low achievers but doesn't benefit high achievers. This describes an interaction effect, where the impact of one variable (tutoring method) depends on the level of another variable (prior achievement). The correct answer is A because the causal effect of tutoring is indeed dependent on students' prior math achievement. Let's examine why the other options are incorrect. Option B suggests the main effect of prior achievement is more important than the tutoring effect, but the question asks specifically about the nature of the tutoring method's causal effect, not which variable is more influential. Option C claims confounding, but since students were randomly assigned to conditions, prior achievement isn't confounding the results - it's a measured factor that moderates the treatment effect. Option D focuses on the overall positive outcome, but this misses the crucial point about how the effect varies by subgroup. When studying experimental design, remember that interaction effects occur when the impact of one independent variable depends on the level of another independent variable. Look for phrases like "effective for some but not others" or "depends on" as clues that you're dealing with interactions rather than simple main effects.

Question 13

An experiment tests if a new study technique improves exam scores. All participants in the experimental group (new technique) are tested in a quiet library in the morning. Due to scheduling constraints, all participants in the control group (old technique) are tested in a busy student center in the afternoon.

The difference in the testing environment (library vs. student center) represents a:

confounding variable that provides an alternative explanation for the results. (correct answer)
source of random error that increases variability in the data.
failure of random assignment to create equivalent groups.
necessary component of the independent variable's operational definition.

Explanation: When evaluating experimental design, you need to identify factors that could systematically bias your results. This question tests your ability to recognize threats to internal validity—the degree to which you can confidently attribute observed effects to your independent variable rather than other factors. The correct answer is A because the testing environment creates a confounding variable. A confound is an extraneous factor that varies systematically with your independent variable and could plausibly explain your results. Here, the study technique (independent variable) is completely entangled with testing location and time of day. If the experimental group performs better, you can't determine whether it's due to the new study technique, the quiet library environment, or testing in the morning when students might be more alert. Option B is incorrect because this isn't random error—it's systematic bias. Random error would occur if participants were randomly assigned to different environments, creating variability but not consistent bias in one direction. Option C misidentifies the problem. The issue isn't with random assignment itself, but with the systematic difference in testing conditions between groups after assignment. Option D is wrong because testing environment isn't part of how the study technique is defined or implemented—it's an uncontrolled external factor. Remember this key principle: confounding variables are the "third variable problem" in experiments. Always scan for factors that differ systematically between groups and could reasonably influence your dependent variable. Strong experimental design controls these variables to isolate the true effect of your manipulation.

Question 14

ensure that the sample of 100 undergraduates is representative of the general population.
increase the likelihood that pre-existing differences in memory ability are balanced between the two groups. (correct answer)
control for situational confounding variables, such as the time of day the experiment is run.
prevent participants' expectations about the new technique from influencing the results.

Question 15

Why is the district's causal conclusion not well-supported by this research design?

The study lacks a control group because all schools received some form of curriculum.
The dependent variable, math score gains, is not an objective measure of learning.
The study only shows a correlation, and correlation does not equal causation.
Pre-existing systemic differences between high-poverty and low-poverty schools were not controlled for. (correct answer)

Question 16

A primary methodological challenge specific to this within-subjects design is:

ensuring the initial equivalence of the 'alone' and 'group' conditions, since individual differences in humor appreciation could be a confound.
the potential for order effects, such as practice or fatigue, to influence the ratings in the second condition. (correct answer)
the difficulty of recruiting a large enough sample to have sufficient statistical power.
the ethical implications of having participants rate jokes without knowing the study's true purpose.

Question 17

The difference in the testing environment (library vs. student center) represents a:

confounding variable that provides an alternative explanation for the results. (correct answer)
source of random error that increases variability in the data.
failure of random assignment to create equivalent groups.
necessary component of the independent variable's operational definition.

Question 18

A company wants to prove its new 'brain-training' game improves fluid intelligence. Participants are randomly assigned to two groups. The experimental group plays the game for 30 minutes a day for four weeks. The control group is instructed to 'continue your daily routine as normal' for four weeks. At the end, the experimental group scores higher on a test of fluid intelligence.

The company's conclusion is most weakened because the control group:

was not given a pretest of fluid intelligence to establish a baseline.
knew they were in the control group, which may have lowered their motivation.
fails to control for placebo effects or the effects of engaging in any structured activity. (correct answer)
was not formed through true random assignment to conditions.

Explanation: The improvement in the experimental group could be due to the game itself, or it could be due to other factors like the expectation of improving (placebo effect), the novelty of the task, or simply the effect of spending 30 minutes a day doing a structured, engaging computer task. A 'no-treatment' control group like this one doesn't account for these alternative explanations. A better design would use an 'active control,' where the control group plays a different, non-brain-training game for the same amount of time. 'A' is a good practice but less critical than the control issue. 'B' is part of the problem, but 'C' is a more comprehensive explanation of the design flaw. 'D' is contradicted by the stem.

Question 19

In this study, which of the following is the independent variable?

The score on the standardized anxiety questionnaire.
The amount of daily screen time reported by participants.
The specific 15-minute daily activity participants were assigned. (correct answer)
The use versus non-use of the mindfulness app.

Question 20

In this experiment, what is the role of the IQ test?

It is a second independent variable being manipulated by the researchers.
It is the primary dependent variable used to measure creativity.
It is a potential confounding variable that was unintentionally introduced.
It is a measured variable used to check the initial equivalence of the randomly assigned groups. (correct answer)