Experimental Design Flashcards
Experimental design
When carrying out an experiment, psychologists must decide on how they are going to use/distribute their participants effectively
Independent groups design
Different participants are used in each condition of the experiment.
• If there are two levels of the IV this means that some participants will take part in the experimental condition, while the other group is the control group
Strength- independent groups
Order design
are avoided – participants only take part in one
condition so they cannot get better/worse between conditions, they cannot get tired and bored
Strength- independent groups- demand characteristics
Are avoided – participants only take part in one
condition, so they are less likely to guess the aim of the study and alter their behaviour accordingly.
Limitation- independent groups
to produce the same amount of data
as repeated measures design (this can be time consuming to recruit more participants)
More participants are required
Limitation- independent groups
Participant variables- a difference between the groups might be
because of the characteristics of the group rather than the manipulation of the DV.
Repeated measures design
The same participants take part in both conditions of the experiment.
• This means that each condition of the experiment includes the same group of participants
Strength- repeated measures
Fewer participants are required- all participants are taking part in all
conditions (therefore less time consuming to recruit participants as don’t need as many
Strength- repeated measures designed
Participant variables are controlled for
– there are no individual differences between the groups as the same people are taking part in both.
Limitation- repeated design measures
Order effects
– the order of the conditions may have an effect on
behaviour. Some people may have improved between conditions, some people may have declined between conditions
Limitation- repeated measures design
Demand characteristics- participants are more likely to work
out the aim of the study as they are taking part in two conditions and therefore may alter their behaviour.
Counterbalancing- repeated measures
An attempt to control for the effects of order effects in a repeated measures design: half of the participants experience the conditions in one order (A then B) and the other half in the opposite order (B then A).
Matched design pairs
Pairs of participants are matched in terms of key variables such as age.
Strength- matched pairs design
Participant variables are reduced
– the researcher has tried to match the
participants as much as possible on important aspects.
Strength- matched pairs
Order effects are avoided
– people only actually take part in one
condition so they cannot get bored, tired or better in between.
Strength- matched pairs
Demand characteristics are reduced
– people are less likely to guess the aim
as they only take part in one condition.
Limitation- matched pairs
Time consuming and expensive
to match participants
Limitation- matched pairs
Individual differences
still occur – the matching of participants can never be
exact so participant variables can still affect the experiment
