Case Study

Explain how the two independent variables in this case study differ in terms of researcher control and participant assignment. How does combining these two types of variables allow the researchers to understand their joint effects?

Case context: A research team wants to study the joint effects of environmental cleanliness and individual trait differences on moral judgments. Inspired by Schnall and colleagues, they design a factorial experiment. They place half of their participants in a sparkling clean testing room and the other half in a room with overflowing trash cans and dirty surfaces. Before starting the task, all participants complete a standardized self-report scale that assesses their level of private body consciousness (their awareness of internal bodily sensations). The researchers want to understand the nature of these two independent variables and why they are combined.

Question: Explain how the two independent variables in this case study differ in terms of researcher control and participant assignment. How does combining these two types of variables allow the researchers to understand their joint effects?

Sample answer: The room cleanliness is a manipulated independent variable, which the researchers actively control and randomly assign participants to (clean vs. messy room). Conversely, private body consciousness is a non-manipulated (measured) independent variable, representing a pre-existing participant trait that cannot be assigned or changed. Combining these variables allows researchers to examine how an environmental state (disgust/cleanliness) interacts with an individual characteristic (private body consciousness) to jointly influence moral judgments.

Key points:

  • Contrast the direct control/random assignment of the room cleanliness variable with the measured nature of private body consciousness.
  • Explain that private body consciousness is a pre-existing participant trait.
  • Explain that combining these variables allows the study of interaction or joint effects between environmental states and personality traits.

Rubric: The response should demonstrate comprehension by: 1. Contrasting the manipulated variable (under researcher control/assignment) with the non-manipulated participant variable (pre-existing trait/measured). 2. Explaining that the factorial combination reveals how situational and individual factors interact or jointly influence the dependent variable.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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