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Selection Effect
A selection effect is a type of confounding variable that occurs when the participants in a treatment group differ from those in a control group in some systematic, pre-existing way. This issue frequently arises in quasi-experimental designs where researchers cannot use random assignment to place participants into conditions. When a selection effect is present, it provides an alternative explanation for the results, making it difficult to confidently determine whether the observed differences in the dependent variable were caused by the experimental treatment or by the inherent differences between the groups.
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Research Methods in Psychology - 4th American Edition @ KPU
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Example of a Quasi-Experimental Study: Sex and Spatial Memory
One-Group Posttest Only Design
One-Group Pretest-Posttest Design
Nonequivalent Groups Design
Example of a Quasi-Experimental Study: Anti-Bullying Program
Selection Effect
Comparison of Internal Validity Across Research Designs
Tuskegee Syphilis Study
Elimination of Directionality Problem in Quasi-Experiments
Applications of Quasi-Experimental Research
Causal Limitations of Quasi-Experimental Research
Which of the following is a key characteristic that distinguishes quasi-experimental research from a true experiment?
Match each feature of a quasi-experimental design with the specific role it plays or the consequence it has on the quality of a psychological research study.
A clinical psychologist evaluates the effectiveness of a new mindfulness-based therapy by providing the treatment to all patients at one clinic while patients at a neighboring clinic receive standard care. Because the researcher is manipulating the treatment but is using pre-existing groups rather than assigning individual patients to conditions by chance, this study is best categorized as a(n) _________ research design.
A psychologist is testing the impact of a new peer-mentoring program in a local high school. Arrange the logical sequence of steps the psychologist would take to conduct a study that follows a quasi-experimental design and evaluates the strength of its causal claims.
A researcher claims that their quasi-experimental study provides the same level of confidence in causal conclusions as a true experiment because both designs involve the manipulation of an independent variable. This evaluative claim is scientifically sound.
Although quasi-experimental research offers more control than purely correlational studies, it generally possesses lower internal validity than a true experiment because it lacks random assignment or counterbalancing.
A researcher evaluates a new educational software by implementing it in one classroom and comparing the results to another classroom that continues with the standard curriculum. Which statement best explains why this quasi-experimental design has lower internal validity than a true experiment, yet still provides more control than a purely correlational study?
A psychology instructor asks students to match scenarios with their corresponding design feature. Match each research description to the quasi-experimental design feature or consequence it applies.
An investigator is analyzing the methodological differences between two research proposals. Study A uses random assignment and counterbalancing, whereas Study B implements a comparison condition using pre-existing groups without random assignment. In analyzing their quality, the investigator concludes that Study B generally possesses lower _____ than Study A.
Evaluate the following research design scenarios based on the standard of internal validity and control established in methodology. Arrange them in order from the design that provides the HIGHEST level of internal validity to the design that provides the LOWEST level of internal validity.
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What type of confounding variable occurs when participants in a treatment group differ from those in a control group in a systematic, pre-existing way?
In a study comparing the effectiveness of two different study methods, if a researcher allows students to choose which method they want to use rather than using random assignment, the study is susceptible to a selection effect.
A selection effect is a threat to internal validity where the participants in one group differ systematically from those in another group before the study starts. Match each research scenario with the specific pre-existing participant characteristic that is responsible for the selection effect.
A researcher offers a voluntary stress-management workshop to employees and compares their stress levels to those of employees who did not sign up. Arrange the following events in the correct logical sequence to illustrate how a selection effect develops and creates a threat to internal validity.
In psychological research, a 'selection effect' is most likely to occur when which of the following happens?
Selection effects occur when groups in a study are fundamentally different before an experiment even begins. Match each core concept with the statement that best explains its relationship to this research challenge.
A researcher concludes that a new exercise program significantly reduces anxiety after comparing a group of fitness-club members who volunteered for the program to a group of non-members who did not. To critically evaluate the internal validity of this study, one must identify that the _____ acts as a confounding variable, as the groups likely differed in their baseline physical health or motivation before the program ever started.
A researcher investigates the effect of a new math tutoring program by comparing the final exam scores of students who voluntarily attended the weekly tutoring sessions to the scores of students who chose not to attend. In this scenario, the study design is susceptible to a selection effect because the students in the treatment group may have had higher pre-existing motivation or academic ability than those in the control group.
A researcher compares the test performance of students who volunteered for a test-prep course to those who did not. Because the students were not randomly assigned, pre-existing differences in motivation between the groups represent a selection effect, which is a type of _____ variable that provides an alternative explanation for the differences in test scores.
A researcher compares a voluntary workplace exercise program to no program and claims the program reduces absenteeism. Order the steps of evaluating this claim to demonstrate how a selection effect invalidates the causal conclusion, starting from identifying the design limitation to the final evaluation of the causal claim.