1. Conducting experiments
Chapter 9

2. Manipulating the independent variable
Setting the stage
Types of manipulations
Straightforward
Uses instruction and stimulus presentation
Staged
Used sometimes to create a psychological state
Tries to replicate an experience that may happen in real life
Employ a confederate (appears to be another participant but is part of the manipulation)

3. Manipulating the independent variable
Strength of the manipulation
To be strong, one should maximize the differences b/w the 2 groups
Important in the early stages of research
Take into account
Likelihood of happening in reality
Ethics
Cost of the manipulation
Resources cost money
Salaries for confederates, printing, pens, setting

4. Measuring the dependent variable
Self report measures
Behavioral measures
Physiological measures

5. Measuring the dependent variable
Sensitivity of the DV
Should be able to detect differences b/w groups
Ceiling effect
Occurs if IV appears to have no effect on the DV only b/c participants quickly reach the maximum performance level
Scores for different conditions are close to the maximum score so no significant differences can occur
To avoid this: Make the task more difficult. Run a pilot study.
Floor effect
Occurs if the task is so difficult that the subject cannot perform well
When a task is so difficult that the experimental manipulation shows little/no effect.
To avoid this: Make the task easier. Run a pilot study

6. Measuring the dependent variable
Multiple measures
Measuring more than one IV
Helps to know if some IVs affects some measures but not others
Remember to counterbalance order of presentation

7. Additional controls Controlling for participant expectations
Demand characteristics
Any feature of an experiment that might inform participants of the purpose of the study
To control use______________
Placebo groups
Led to believe treatment is being given when it is not
Tests if treatment is working
Ethical implications

8. Additional controls Controlling for experimenter expectations
Experimenter bias – researcher develops expectations of how participants should respond
Solutions
Be consistent with all participants
Run all conditions simultaneously
Automate procedures
Use “blind” experimenters
Single blind:
Double blind:

9. Additional considerations
Research proposals
Have a literature review
Tries to explain why the research is being done and what questions the research is trying to answer
Includes plans for analysis
Used in grant applications
Get input from outside parties
Pilot studies
Trial runs to see if study will work smoothly

10. Additional considerations
Manipulation check
An attempt to directly measure whether the IV manipulation has the intended effect on the participants
Useful in the pilot study to see if the right effect is created
Also useful in the experimental study
Debriefing
Experimenters interact with the participant to discuss the ethical and educational implications of the study
Experimenters can learn more about what participants were thinking
Experimenters ask participants to refrain from discussing details of the study with others (future participants).

11. Analyzing, interpreting and communicating results
Analyses
Run the appropriate statistics
Professional meetings
APA, SFN, SPR
Talk to other researchers about the latest research
Journal articles
Research is subjected to peer review
Allows research to be distributed widely
Accepts high quality work