Lecture 3 - Principles of Experimental Designs II Flashcards
Definition of independent variable
- The experimental factor(s) that distinguishes your groups (manipulated variable)
- Has to have at least 2 levels
What is a true experiment
When the IV is being directly manipulated (prediction AND explanation)
What is a quasi experiment?
When the independant variable is NOT being directly manipulated (prediction but NOT explanation)
If quasi experiment, cannot conclude causal relationship
If you have IV (X), and you observe result Y, what are the 4 possible explanations
- X does cause Y
- Y causes X
- Some 3rd factor Z causes both X and Y
- Chance
What are confounding variables?
If participants are not randomly assigned to condition, there may be many differences between groups other than the IV
What is a control group?
- Comparison group
- Differs from experimental groups by the absence of the experimental treatment
What is the placebo effect?
A treatment that appears real, but is designed to have no theraputic benefit
What is a single blind study?
When only the experimenter knows the condition the participant is assigned to
What is a double blind study?
When neither participant nor experimenter knows the condition the participant is assigned to
What are demand characteristics?
Cues in a new situation that people interpret as “demands” for a particular behaviour
What is a between subject design?
Where each participant is tested in only one level of the IV
What is a within subject design?
Where each subject is tested in every level of the IV
What is the order effect?
Order in which participants experience IV levels can cause issues in a within subject design
What is counterbalancing?
A way to eliminate the order effect. Each treatment condition is equally exposed to the practice effects and demand characteristics inhernt in the within subject design
What are control variables?
An extraneous variables that are held constant during an experiment
