Cozby Chapter 9 -- Conducting Experiments
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

Independent Variable
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?

Dependent Variable
Types of measures
Behavioral measures
Physiological measures

Avoid floor and ceiling effects
Multiple measures, costs, ethics?
Additional Controls
Participant expectations
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?
Manipulation Check
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.

Ethical reasons
Educational reasons
Practical reasons