Cozby Chapter 9 -- Conducting Experiments
What things need to be considered?
Selecting Research Participants
Often use a convenience sample – e.g. college students
This is not an issue for internal validity, if the study is well-designed
It is an issue for external validity – generalizing to broader population
Setting the stage for participants
Types of Manipulations
Staged – most common with social psychology, use of confederates
Strength of Manipulation
Amount of difference between conditions
The independent variable should have a good chance of influencing participants
Most important in early (exploratory) stages of research
How much does it cost (in terms of cost/benefit) to manipulate the IV and maintain ethics?
Types of measures
Avoid floor and ceiling effects
Multiple measures, costs, ethics?
Demand characteristics give clues to the true hypothesis of an experiment
Placebo effects and placebo groups
Experimenter expectations - The “E” variable (Rosenthal effect).
Blind and Double Blind experiments
Other controls may be needed to account for alternative explanations
Why should a research proposal be developed?
Justify purpose?, What answers expected?, Organize thinking; provide detail of procedures; and a plan for analysis
Pilot Study - What is it?
Make sure the IV is having its intended effect on participants
Using Computers to Conduct Research
Provide tools for presenting stimuli and/or manipulating IV and record data.