Based on the concept of confounding variables described in the text, explain why the student's causal conclusion is invalid, and diagnose how the loud noise functioned in this design.
Case context: A psychology student is replicating the lighting and productivity study. During the bright-light session, a drilling project begins next door, creating a loud noise. During the dim-light session, the drilling project is completed and it is completely quiet. The student finds that workers are more productive under dim lights and concludes that dim lighting causes higher productivity.
Question: Based on the concept of confounding variables described in the text, explain why the student's causal conclusion is invalid, and diagnose how the loud noise functioned in this design.
Sample answer: The student's causal conclusion is invalid because the loud noise is a confounding variable. Since the noise was present only during the bright-light condition and absent during the dim-light condition, it varied systematically with the independent variable (lighting). This systematic variation provides an alternative explanation for the difference in productivity, meaning the researcher cannot determine if lighting or noise caused the productivity changes.
Key points:
- Diagnose the loud noise as a confounding variable in this specific setup.
- Explain that the noise varied systematically with the lighting conditions (bright vs. dim).
- Identify that the noise provides an alternative explanation for the productivity differences.
- Conclude that a causal conclusion about the effect of lighting cannot be drawn.
Rubric: The response must demonstrate comprehension by identifying the noise as a confounding variable. It must explain that because the noise only occurred in one condition, it varied systematically with the lighting. Finally, it must explain that this systematic variation provides an alternative explanation, preventing a valid causal conclusion.
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Research Methods in Psychology - 4th American Edition @ KPU
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