Psych 231 Lectures: Week 6
Week 6, Day 1: Exam 1
Week 6, Day 2: Designing Experiments
So you want to do an experiment?
- First get your theory.
- What is the behavior/cognitive process that you want to examine?
- What do you think affects that behavior/cognitive process?
- Next you need to derive predictions from the theory.
- These should be stated as hypotheses.
- In terms of conceptual variables (control, independent, and dependent)
- Now you need to operationalize your variables in terms of how they will be controlled, manipulated, and measured in the experiment
- Be aware of the underlying assumptions that link the conceptual variables to their operational variants
Can you control your extraneous variable(s)
- Can you keep them constant?
- Should you make them random variables?
- Two things to watch out for:
- Experimenter bias - the experimenter may influence the results (intentionally and unintentionally)
- Clever Hans - a mathematically inclined horse. It turned out that his trainer was giving (unintentional) cues to the horse that told the horse when to stop counting.
- One solution is to keep the experimenter "blind" as to what conditions are being tested
- Demand characteristics - cues that allow the participants to figure out what the experiment is about, influencing how they behave
Choosing your independent variable(s)
Method of manipulation:
- Subject manipulation
- Event manipulation
- Stimulus manipulation
- Instructional manipulation
Choosing the right range of your independent variable
- Review the literature
- do a pilot experiment
- pick a large enough range to show the effect
- be realistic
- consider the costs, your resources, your limitations
- pick levels found in the "real world"
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