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Nonequivalent Groups
When participants in a between-subjects experiment are placed into conditions without the use of random assignment, the resulting groups will likely be dissimilar in various ways. Because these groups possess inherent, pre-existing differences from the outset, researchers consider them to be nonequivalent.
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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.
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Nonequivalent Groups Design
In a between-subjects experiment, what term describes groups that are formed without the use of random assignment and thus possess inherent, pre-existing differences from the outset?
If a researcher assigns participants to conditions based on whether they sign up for a morning or afternoon session, the resulting groups are considered nonequivalent.
A psychologist is conducting several research studies comparing existing groups of people without using random assignment. Match each research scenario to the specific pre-existing difference that would lead the researcher to classify the groups as nonequivalent.
A researcher evaluates a new 'Memory Booster' supplement by comparing a group of students who volunteered for a 6:00 AM trial to a group of students who did not volunteer. Arrange the following statements to logically trace how this lack of random assignment creates 'nonequivalent groups' and leads to ambiguous results.
A clinical psychologist is designing a research protocol to compare the recovery rates of patients in two different psychiatric clinics. To construct a study that specifically utilizes nonequivalent groups, which of the following procedures should the psychologist follow?
In a between-subjects experiment, nonequivalent groups are formed when researchers use random assignment to ensure that the groups are as similar as possible from the outset.
To demonstrate your understanding of group composition in psychological research, match each research-design concept with the statement that best describes it.
A psychologist attempts to test a new memory strategy by comparing students in an 8:00 AM class to those in a 2:00 PM class. When assessing the rigor of this research, a critic would point out that because students were not randomly assigned, the researcher is comparing _____ groups, making any conclusions about the strategy's effectiveness highly questionable.
An educational researcher compares the reading comprehension scores of students in two pre-existing classrooms, where one class receives a new reading intervention and the other does not. In analyzing the design, the researcher notes that because students were not randomly assigned to the classrooms, the groups likely differ on variables such as baseline reading ability and socioeconomic status. Because of these pre-existing differences from the outset, the researcher must analyze these groups as _____ in their study.
A psychologist evaluates a study claiming a new exercise program reduces anxiety. The study compared a group of volunteers who chose the exercise program to a control group who preferred a sedentary lifestyle. Order the steps a critic should take to evaluate the internal validity of the psychologist's claim, starting from identifying the group assignment method to rendering a final judgment on the causal conclusion.