In-Depth Notes on Experiments

Experiments

• Definition of Experiments
  • Involves taking action and observing the consequences of that action.

Topics Appropriate to Experiments

• Ideal for projects involving:
  • Limited and well-defined concepts.
  • Hypothesis testing: better for explanatory purposes.
  • Small group interaction.

The Classical Experiment

• Major Components:
  1. Independent and Dependent Variables
  • Independent Variable: Stimulus, cause (present or absent).
  • Dependent Variable: Effect that is measured.
  1. Pre-testing and Post-testing
  • Pre-testing: Measurement of the dependent variable before exposure to the independent variable.
  • Post-testing: Measurement of the dependent variable after exposure to the independent variable.
  1. Experimental and Control Groups
  • Experimental Group: Receives the experimental stimulus.
  • Control Group: Does not receive the experimental stimulus; must resemble the experimental group in all other aspects.

Illustrative Example

• Experiment Process:
  1. Administer the experimental stimulus (e.g., a film).
  2. Measure the dependent variable before and after to compare results.

The Hawthorne Effect

• Influence of the researcher's presence on participants' behavior, potentially skewing results.

The Double-Blind Experiment

• Neither participants nor experimenters know which group (experimental or control) the participants are assigned to, minimizing bias.

Selecting Subjects

• Role of College Students:
  • Generalizability of results raised by the demographic.
• Sampling Techniques:
  • Probability Sampling: Ensures all subjects have an equal chance of being selected.
  • Randomization: Assigning subjects randomly to groups to minimize bias.
  • Matching: Pairs of subjects are matched based on similarities; one member is assigned to the experimental group, the other to the control group.

Variations on Experimental Design

1. One-shot Case Study:
   • A single group is measured after exposure to a stimulus.
2. One-group Pre-test Post-test Design:
   • A pre-test is given before the stimulus; lacks a control group.
3. Static-group Comparison:
   • Experimental and control groups exist, but no pre-test.

Validity Issues in Experimental Research

• Internal Validity:
  • The extent to which the experimental results accurately reflect what occurred in the experiment.
  • Potential Sources:
  • History, maturation, testing effects, instrumentation issues, statistical regression, selection bias, experimental mortality, causal time order, treatment diffusion or imitation, compensatory strategies, etc.
• External Validity:
  • Generalizability of the experimental findings to the broader population or real-world settings.

Examples of Experimentation

• Field Experiments: Conducted in natural settings rather than labs.
• Web-Based Experiments: Less emphasis on representative samples; volunteers may be used.
• Natural Experiments: Occur in uncontrolled settings, taking advantage of existing conditions.

Strengths and Weaknesses of the Experimental Method

• Strengths:
  • Isolation of the impact of the experimental variable.
  • Ability to replicate the study.
• Weaknesses:
  • Artificiality of laboratory settings which may not reflect real-world scenarios.

Quiz Questions

1. In the simplest experimental design, subjects are measured as a/n variable exposed to a/n variable.
   • Answer: C. Independent; Dependent
2. _ groups are groups of subjects to whom an experimental stimulus is administered.
   • Answer: B. Experimental
3. _ is a technique for assigning experimental subjects to experimental and control groups randomly.
   • Answer: C. Randomization
4. Experiments are especially well-suited for research involving:
   • Answer: D. All of the above choices
5. _ refers to the possibility that the conclusion drawn may not accurately reflect what has gone on in the experiment itself.
   • Answer: B. Internal validity
6. Which is the chief advantage of a controlled experiment?
   • Answer: D. The experimental variable is isolated.