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Equivalent Groups
In a between-subjects experiment, when researchers utilize random assignment to allocate participants to different conditions, the resulting groups are expected to be highly similar to one another. Because these groups lack systematic pre-existing differences, researchers consider them to be equivalent.
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Research Methods in Psychology - 4th American Edition @ KPU
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Random Assignment
Advantages of Between-Subjects Experiments
Independent-Samples t-Test
One-Way ANOVA
Within-Subjects Experiment
Matched-Groups Design
Examples of Between-Subjects Experiments
Example of Lack of Context in Between-Subjects Designs
Combining Between-Subjects and Within-Subjects Designs
Equivalent Groups
Nonequivalent Groups
Which of the following best describes a between-subjects experiment?
In a between-subjects experiment, researchers test each participant across every level of the independent variable to directly compare their individual responses.
A researcher is conducting a between-subjects experiment to test if '8 hours of sleep' versus '4 hours of sleep' affects cognitive performance on a memory task. Arrange the steps of this specific study in the correct chronological order.
A researcher investigates whether a new font improves reading speed. They assign 50 participants to read a text in 'Times New Roman' and another 50 participants to read the same text in 'OpenDyslexic'. Match each aspect of this study to the structural logic of a between-subjects experiment.
You are tasked with creating a research protocol to investigate whether a 'Gamified' exercise app increases user motivation more than a 'Standard' exercise app. To avoid 'carryover effects'—where the experience with one version of the app might influence the user's perception or performance with the other—you decide to implement a between-subjects experiment. Which of the following plans should you develop to successfully fulfill this design requirement?
A researcher is evaluating whether to use a within-subjects or a between-subjects design for a study on a permanent educational intervention. They determine that a(n) _____ design is the only valid choice because the intervention results in an irreversible change, making it impossible for the same participants to serve in both the experimental and control conditions.
An experimental design in which each participant is exposed to only a single level of the independent variable is called a(n) _____ experiment.
A clinical researcher measures each participant's stress level at three time points: before a mindfulness program begins (Week 0), after four weeks of training (Week 4), and after eight weeks of training (Week 8). Every participant completes the same single program. The researcher argues that this is a between-subjects design because each participant is assigned to only one program. This argument is correct.
A researcher studies whether type of reward (monetary payment, verbal praise, or no reward) affects how long elementary school children persist on a difficult puzzle. One group receives money after each puzzle attempt, a second group receives verbal praise, and a third receives nothing. No child participates in more than one condition. Match each term to the description that correctly identifies its role in this study.
A research team wants to test whether a new anti-anxiety drug (Drug A), an established drug (Drug B), or a placebo reduces self-reported anxiety in adults with generalized anxiety disorder. They must design the study and analyze the data responsibly. Arrange the following decisions and actions in the order that best reflects sound research practice for a between-subjects experiment.
Define a between-subjects experiment. In your definition, clarify how participant exposure to the independent variable distinguishes this design from a within-subjects design.
Explain why this study is classified as a between-subjects design. Additionally, explain how stable individual differences among the participants in the separate groups affect the within-groups variability () and the resulting statistic in the One-Way ANOVA.
Suppose you are designing a between-subjects experiment to test the effects of two different teaching methods on student learning. What must you do when assigning participants to the two conditions, and what is the primary methodological reason for doing so regarding participant variables?
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When researchers use random assignment to allocate participants to different conditions, they expect the resulting groups to lack systematic pre-existing differences. What is the term used to describe these highly similar groups?
When researchers create 'equivalent groups' for an experiment, it means the groups are expected to be similar on average even though the individual participants within them are not identical.
A researcher is conducting a study comparing how different types of background noise affect reading comprehension. Order the steps the researcher should take to ensure they are starting the experiment with equivalent groups.
In psychological research, achieving control requires researchers to analyze the relationship between their assignment methods and the resulting characteristics of their conditions. Match each concept to the functional role it plays in establishing a valid comparison between groups.
In experimental research, what is the defining characteristic of 'equivalent groups'?
Arrange the logical stages involved in establishing 'equivalent groups' for a between-subjects experiment.
A researcher evaluates a between-subjects experiment and discovers that participants were assigned to conditions based on their level of prior experience with the task. The researcher must conclude that the study fails to utilize _____ groups because this method allowed for systematic pre-existing differences to influence the results.
A researcher randomly assigns 40 participants to either a treatment group or a control group in a between-subjects experiment. A skeptical colleague argues that the two groups cannot truly be 'equivalent' because every individual participant is unique and no two people are alike. This objection correctly challenges the logic of equivalent groups in between-subjects experimental design.
A researcher designing a between-subjects experiment must understand how key concepts relate to establishing—or undermining—equivalent groups. Match each term to the role it plays in that process.
A graduate student presents a between-subjects study in which participants who were already experiencing high stress were allowed to choose whether they joined the stress-reduction workshop group or the no-treatment control group. A faculty advisor evaluating the study concludes that any difference in post-study stress scores cannot be confidently attributed to the workshop alone, because the two groups are _____, meaning pre-existing participant differences—rather than the treatment itself—could explain the observed outcome.