Experimental design Flashcards
Two conditions involved in a basic experiment?
- Control condition = variables held constant
- Experimental condition = IV is manipulated
Types of experimental design?
- Independent groups
- Repeated measures
- Matched pairs
Independent groups design
Ppts take part in only one condition of the experiment.
- Lab experiment - randomly allocated participants so ppt variables balance out across conditions.
How to reduce the effect of participant variables on results?
Increasing the size of the sample - extreme scores have less effect when there are more scores
Repeated measures design
Each participant takes part in all conditions of the experiment
How to deal with order effects
- Counterbalancing
- Randomization
Counterbalancing
Reduces order effect - ensuring ppt variables occur with equal frequency in all conditions of the experiment
Randomization
Using chance to decide the order in which ppts experience the experimental or control condition when using a repeated measures design.
- Also to decide the order of use of stimuli.
Matched pairs design
Ppts in each condition of the experiment are matched according to important variables
Confounding variable
Uncontrolled variable that has an effect on the DV
Strengths of the independent group’s design? 3 marks
- No order effects
- Both conditions can be tested simultaneously = saving time and effort.
- Ppts take place in only one condition = reduced demand characteristics and investigator effects
Limitations of the independent groups’ design? 2 marks
- Ppts variables may affect results
- Twice as many ppts needed
Strengths of repeated measures design? 2 marks
- Uses fewer ppts = saves time
- Ppts variables are not a concern
Limitations of repeated measures design? 2 marks
- Risk of order effects
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Strengths of matched pairs design? 2 marks
- Good control of participant variables
- Elimiates order effects
