Experimental designs Flashcards
Define experimental design.
The different ways in which participants can be organised in relation to experimental conditions.
What is an independent groups design?
Two separate groups of participants experience two separate conditions of an experiment. E.g one group experiences condition A and one condition B then the two groups would be compared.
What is a repeated measures design?
All participants take part in all conditions of the experiment. The two scores from both conditions would be compared to see if there was a difference.
What is a matched pairs design?
Participants are paired together on a variable or variables relevant to the experiment then one of the participants in the pair is allocated to condition A and one to condition B. E.g in a memory study participants may be matched on their IQ.
Limitations of an independent groups design?
The participants who occupy the different groups are not the same in terms of participant variables. These differences may act as a confounding variable.
How do we deal with the problems of independent groups?
Random allocation.
What is random allocation?
Ensures that each participant has the same chance of being in one condition as any other.
Limitation of repeated measures.
Each participant has to do at least two tasks and the order of these tasks may be significant. E.g they may get bored or fatigued which may cause deterioration in performance on the second task or performance could improve through the effects of practice.
Participants may work out the aim of the study when they experience all conditions of the experiment so demand characteristics tend to be a feature.
Strength of repeated measures.
Participant variables are controlled and fewer participants are needed.
How do we deal with the issues of repeated measures?
Counterbalancing
What is counterbalancing?
Half of the participants experience conditions in one order and the other half in the opposite order.
What is referred to as the ABBA technique?
Counterbalancing.
Strength of matched pairs.
Participants only take part in a single condition so order effects and demand characteristics are less of a problem.
Limitation of matched pairs.
Participants can never be matched exactly even when identical twins are used, there will still be some important differences between them which may affect the DV.
Matching may be time-consuming.
Explain how random allocation may be carried out.
Allocate each participant with a number and place these numbers in hat/random number generator.
Generate one number, allocate this person to condition a.
Generate the next number, allocate them to condition b.
