Research Methords : Experimental Designs Flashcards
What is an experimental design
The different ways in which participants can be organised in relation to experimental conditions
What is a key acronym to remember the different types of experimental design
R - REPEATED
I - INDEPENDENT
M - MATCHED PAIRS
What is independent groups design
Participants are allocated to different groups where each group represents one experimental condition
If there are two levels of the IV participants only experience one level of the IV only
What happens after independent groups design
The performance of two groups will be compared
What is repeated measures design
All participants take part in all conditions of the experiment
Example would be each participant experiences condition 1 and then condition 2 or vice versa
What happens after repeated measures design
The two mean scores from both conditions would be compared to see if there was a difference
What is matched pairs design
Pairs of participants are first matched on some variables that may affect the DV
Then one member of the pair is assigned to condition A and the other to condition B
Example of matched pairs design
A memory study - participants might be matched on IQ as this might be a good indication of their ability to recall information.
The two participants with the first and second IQ scores would be paired together.
Then one person from each pair would be allocated to a different condition of the experiment.
This is an attempt to control CONFOUNDING VARIABLES AND PARTICIPANT VARIABLES
STRENGTHS of independent groups design
LESS ECONOMICAL than repeated measures as each participant contributes as a single result only.
Twice as many participants would be needed to produce equivalent data to that collected in a repeated measures design.
ORDER EFFECTS NOT A PROBLEM
PARTICIPANTS LESS LIKELY TO GUESS AIMS
LIMITATIONS of independent groups design
Participants who occupy in different groups are not the same in terms of participant variables
So PARTICIPANT VARIABLES may effect IV
Differences may act as a confounding variables so reduce VALIDITY of findings
How to deal with limitation of indecent groups design
RANDOM ALLOCATION
What is random allocation
An attempt to control for participant variables in an independent groups design which ensures that each participant has the same chance of being in one condition as any other
LIMITATIONS of repeated measures
Each participant has to do at least two tasks - ORDER EFFECTS ARE A PROBLEM
Repeating two task could create BOREDOM OR FATIGUE so deterioration in performance on second task
DEMAND CHARACTERISTICS
STRENGTHS of repeated measures design
Participant variables are controlled so higher validity
Fewer participants needed so less time spent recruiting them
What is COUNTERBALANCING
An attempt to control for order effects in repeated measures design
Half the participants experience the conditions in one order and the other half in the opposite order
What is counterbalancing sometimes referred to as
ABBA technique
Where ever participant does four trials, A,B,B,A
Counterbalancing does not remove or prevent the problem but attempts to balance out the effects
LIMITATIONS of matched pairs
Time consuming
Expensive
Particularly if a pre-test is required
SO LESS ECONOMICAL THAN OTHER DESIGNS
Participants can never be matched exactly - there will still be important differences which may affect the DV
STRENGTHS of matched pairs
Participants only take part in one condition so ORDER EFFECTS AND DEMAND CHARACTERISTICS ARE NOT A PROBLEM
