1. Chapter 14 Cooper and Schindler
Experimentation
Chapter 14
Cooper and Schindler

2. What is Experimentation?
Causal method
Allow the researcher to alter systematically the variables of interest and observe what changes follow
Experiments are studies involving intervention by the researcher beyond that requires for measurement
The researcher manipulates the independent variable or explanatory variable and then observes whether the hypothesized dependent variable is affected by the intervention

3. Advantages
The researcher’s ability to manipulate the independent variable
Contamination from extraneous variables can be controlled more effectively than in other design
The convenience and cost of experimentation are superior to other methods
Assemble combinations of variables for testing

4. Disadvantages The artificiality of the laboratory
Generalization from nonprobability samples can pose problems despite random assignment
Many applications of experimentation far outrun the budgets
Experimentation is most effectively targeted at problems of the present or immediate future
Ethical problems

5. Conducting An Experiment
Select relevant variables
Specify the level(s) of the treatment
Control the experimental environment
Select and assign the subjects
Pilot-test, revise, and test
Analyze the data

6. Selecting Relevant Variables
Translate an amorphous problem into the question or hypothesis that best states the objectives of the research
Investigative questions and additional hypotheses can be created to address specific facets of the study or data that need to be gathered

7. Specifying the Levels of Treatment
The treatment levels of the independent variable are the distinctions the researcher makes between different aspects of the treatment condition
A control group could provide a base level for comparison
Experimental group

8. Ways to Assign Subjects
Random Assignment
Matching Assignment
Quota matrix

9. Controlling the Experimental Environment
The need for control
Extraneous variables have potential for distorting the effect of the treatment on the dependent variable and must be controlled or eliminated
Environmental control
Holding constant the physical environment of the experiment
Blind
Subjects do not know they are receiving the experimental treatment
Double blind
The experimenters do not know they are giving the treatment to the experimental group or to the control

10. Choosing the Experimental Design
Preexperimental designs
True experimental designs
Field experiments

11. Preexperimental Designs
One-shot case study
One-group pretest-posttest design
Static group comparison

12. True Experimental Designs
Pretest-posttest control group design
Posttest-only control group design

13. Operational Extensions of True Designs
Completely randomized designs
Randomized block design
Latin square
Factorial design
Covariance analysis

14. Field Experiments: Quasi- or Semi-Experiments
Non Equivalent Control Group Design
Separate Sample Pretest-Posttest Design
Group Time Series Design

15. Selecting and Assigning Subjects
The subjects selected for the experiment should be representative of the population
Random assignment to the groups is required to make the groups as comparable as possible with respect to the dependent variable
When it is not possible to randomly assign subjects to groups, matching may be used
Some authorities suggest a quota matrix

16. Pilot Testing, Revising, and Testing

17. Analyzing the Data

18. Validity in Experimentation
Internal validity
Do the conclusions we draw about a demonstrated experimental relationship truly imply cause?
External validity
Does an observed causal relationship generalize across persons, settings, and times?

19. Threats to Internal Validity
History
Maturation
Testing
Instrumentation
Selection
Statistical Regression
Experiment mortality

20. External Validity The reactivity of testing on X
Interaction of selection and X
Other reactive factors

21. Experimental Research Design
Preexperimental designs
One-shot case study
One-group Pretest-posttest design
Static group comparison
True experimental design
Pretest-posttest control group design
posttest-only control group design
Extensions of true experimental designs
Completely randomized design
Randomized block design
Latin square design
Factorial design