Experimental design and control Flashcards
What is experimental design?
How you allocate your participants
What are the three types of experimental design?
- Repeated measures design
- Independent groups design
- Matched pairs design
Describe repeated measures design
All participants experience all conditions of the experiment (all levels of the IV) i.e. the same people are each in condition.
What are the advantages of repeated measures design?
- No participant variables (individual differences) as the same people are measured in each
condition. - More data produced with fewer participants.
What are the disadvantages of repeated measures design?
- Order effects – if all participants complete condition 1 then condition 2 the results could be hindered. They could end up doing worse in the second condition because of tiredness or boredom (negative order effect) or end up doing better due to practising/learning the task (positive order effects). HOWEVER, Counterbalancing can be used to solve this – involves half the participants doing condition 1 then 2 and the other half doing 2 then 1 L
- more time-consuming.
- Chance of demand characteristics.
Describe independent groups design
Participants only experience one condition of the experiment (one level of the IV) i.e. different people in each condition.
What are the advantages of independent groups design?
- Minimal order effects as each person only doing 1 condition.
- No demand characteristics as no repetition so they can’t guess the aim of study.
- Saves time
What are the disadvantages of independent groups design?
- More participants are required.
- Participant variables – individual differences could impact the DV without researchers realising.
Describe Matched pairs design
Pairs of participants are matched on (participant) variables which may affect the DV e.g. age, gender etc. One member of each pair is randomly allocated to each condition.
What are the advantages of matched pairs design?
- Minimal order effects
- No demand characteristics
- Participant variables aren’t much of an issue due to prior matching.
What are the disadvantages of matched pairs design?
- More time needed
- Challenging and costly to find precise matches
How are experiments controlled?
- Random allocation
- Counterbalancing
- Standardisation
- Randomisation
Describe random allocation
Aims to control participants across conditions - equal chance of being in each condition e.g. all 20 names of students put into a hat. The first 10 picked out will be in A and the remaining 10 will be in B.
Describe counterbalancing
Attempts to control for order effects in repeated measures. Half do A then B and the other half do B then A. Reduces order effects but does not eliminate them.
