Imagine a school principal assigns students to classrooms based on behavior, placing students who need stronger discipline into one class and highly motivated students into another. If a researcher uses these pre-existing classes to test a new educational program without random assignment, apply the concept of confounding variables to explain in one to three sentences how this assignment method threatens the internal validity of the study.
Question: Imagine a school principal assigns students to classrooms based on behavior, placing students who need stronger discipline into one class and highly motivated students into another. If a researcher uses these pre-existing classes to test a new educational program without random assignment, apply the concept of confounding variables to explain in one to three sentences how this assignment method threatens the internal validity of the study.
Sample answer: Because students were not randomly assigned, preexisting differences in student motivation and behavior will differ systematically between the two classrooms. These factors act as confounding variables because they could independently explain any differences in final scores, making it impossible to determine if the new educational program caused the outcome.
Key points:
- Applying the concept of confounding variables to systematic differences in student assignment.
- Explaining that these preexisting differences offer alternative explanations for the outcome.
- Concluding that internal validity is threatened because the program's effect cannot be isolated.
Rubric: Full credit is awarded if the response applies the concept of confounding variables by: (1) noting that non-random assignment creates systematic differences in student motivation/behavior, and (2) explaining that these differences serve as alternative explanations that prevent attributing the outcome to the educational program.
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Imagine a school principal assigns students to classrooms based on behavior, placing students who need stronger discipline into one class and highly motivated students into another. If a researcher uses these pre-existing classes to test a new educational program without random assignment, apply the concept of confounding variables to explain in one to three sentences how this assignment method threatens the internal validity of the study.