In-Depth Notes on One-Factor Experiments in Psychology

Chapter 12: More About One-Factor Experiments

  • This chapter focuses on the principles of conducting one-factor experiments to establish causation in psychological research.

Steps in the Research Process

  • The research process consists of several key steps:
    • Step 1: Choosing a research question
    • Step 2: Conducting a literature review
    • Step 3: Developing a hypothesis
    • Step 4: Designing the study
    • Step 5: Conducting the study
    • Step 6: Analyzing the data
    • Step 7: Reporting the results

Learning About Causation Through Manipulation and Control

  • Key Concepts:

    • Experimental research design uniquely features manipulatable variables, allowing researchers to control their administration.
    • The participant’s characteristics should not affect how the variable is administered.

  • Internal Validity:

    • Manipulation of variables enhances the study's internal validity.
    • Extraneous factors (e.g., confounding variables) can lead to decreased internal validity and create a third-variable problem.
    • Researchers must actively control for these extraneous factors to ensure validity.

Keys to Experiments

  • Fundamental Principles:
    • No significant differences: Groups should not differ initially in significant ways.
    • Random assignment: Essential to mitigate pre-existing differences among participants. This ensures any observed effects are due to the independent variable (IV).
    • Controlled conditions: Must maintain consistent conditions except for the IV.
    • Designation of significant differences: Significant results at the end of a study can allow for conclusions of causation.

Confounding Variables

  • Variables that can interfere with the conclusions drawn from an experiment:
    • Differences in study conditions
    • Variations between experimenters
    • Timing of the study
    • Specific conditions of the IV (e.g. placebo effects)

Types of Experimental Designs

Between-Subjects Design
  • Each participant experiences only one level of the IV. Levels are randomly assigned to participants.
    • Example: Participants play a gambling task under either high or low tempo music.
Within-Subjects Design
  • Each participant experiences all levels of the IV. Scores are compared across different conditions.
    • Example: Participants oscillate between high and low tempo music during the gambling task.
    • Order effects may impact results; thus, controlling this is crucial.

Order Effects in Within-Subjects Experiments

  • Participant performance could be influenced by the order in which conditions are experienced. For example:
    • Performing an easy task followed by a hard task could affect perceived difficulty.
    • Counterbalancing is used to mitigate this effect, where different groups are assigned to different orders of conditions

Experiment Control Comparison

Between-Subjects vs. Within-Subjects
  • Example Between-Subjects: Examining the effect of different types of music on memory by assigning participants randomly to groups with varying background music.
  • Example Within-Subjects: Participants receive all types of music, potentially impacting how they perform based on the order.

Chapter Summary

  • Experiments are characterized by an independent variable that is deliberately manipulated.
  • They are the optimal method for establishing causal relationships in research.
  • Manipulation enhances the internal validity of the study, solidifying findings related to causation.