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Explain how the uncontrolled background music and weather serve as extraneous variables in this scenario, and discuss how the lack of control over these variables affects the study's internal validity.
Case context: A researcher wants to study the effect of ambient lighting on social interaction in a public coffee shop. She randomly assigns different days to either dim, warm lighting or bright, fluorescent lighting (the independent variable). She observes and records the average duration of conversations between patrons. However, she struggles to control the volume of background music, which varies depending on the barista on duty, and the outdoor weather, which fluctuates from sunny to rainy.
Question: Explain how the uncontrolled background music and weather serve as extraneous variables in this scenario, and discuss how the lack of control over these variables affects the study's internal validity.
Sample answer: In this scenario, background music and weather are extraneous variables because they are uncontrolled factors that could influence conversation duration independently of the ambient lighting. Because the researcher struggles to control these variables, the internal validity of the experiment decreases. Without high control over these extraneous variables, the researcher cannot confidently conclude whether the changes in conversation duration were caused by the lighting manipulation or by the varying music and weather.
Key points:
- Background music and weather are extraneous variables that can influence conversation duration.
- A lack of control over extraneous variables threatens the study's internal validity.
- High internal validity requires establishing that the independent variable, rather than extraneous factors, caused the observed effects.
Rubric: Full credit is awarded if the response correctly explains that music and weather are extraneous variables because they can influence the dependent variable (conversation duration) outside of the manipulated lighting. The student must also explicitly connect the low control over these variables to a reduction in internal validity, demonstrating comprehension that internal validity depends on the level of control achieved.
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Research Methods in Psychology - 4th American Edition @ KPU
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