Experimental design Flashcards
What is experimental design?
This refers to how participants are allocated to the different conditions (or IV groups) in an experiment.
What is the independent groups design?
Different participants take part in different conditions. They are usually allocated randomly to these conditions.
What is the repeated measures design?
Each participant is tested in each condition of the experiment.
What is the matched pairs design?
Different but similar participants are used in each condition. They are matched on variables relevant to the study. Monozygotic twins can be good for this as they are genetically perfectly matched.
Strengths of independent groups
Avoids order effects (such as practice or fatigue) as people only participate in one condition only.
Avoids demand characteristics as people are less likely to guess the aim.
Limitations of independent groups
More people are needed than with the repeated measures design (more time consuming.
Differences between participants in the groups may affect the results (participant variables).
Strengths of repeated measures
As the same participants are used in each condition, participant variables are reduced.
Fewer people are needed.
Limitations of repeated measures
There may be order effects. This can be controlled by counterbalancing.
Participants may guess the aims and change their behaviour (demand characteristics).
Strengths of matched pairs
Reduces participant variables because the researcher has tried to pair up the participants so that each condition has people with similar abilities and characteristics.
Avoids order effects, and so counterbalancing is not necessary.
Limitations of matched pairs
If one participant drops out, then you lose two participants data.
It’s very time consuming trying to find closely matched pairs.
Impossible to match people exactly, even identical twins.
