Experimental designs

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Psychology unit 4 research methods revision
Experimental designs
Independent samples- different participants used in each condition
No order effects such as practice and fatigue as participants only do the
experiment once. Practice is when participants do better in the 2nd
condition as they are more familiar with what to do. Fatigue is when
participants get bored with the experiment in the 2nd condition and so won't
try as hard as they did in the 1st condition.
Reduces the likelihood of demand characteristics as the participants only
do the experiment once.
Individual differences are more likely as one group may just be naturally
better than the other group making this extraneous variable more likely. In
order to reduce individual differences, participants are randomly allocated
to the 2 groups
Matched pairs- participants are pre-tested on variables that are important to the
study. The pairs of similar participants are formed and one person from each pair
is put into each condition
Minimises individual differences by balancing them out
No order effects as each group only does the experiment once
It can be hard to match people perfectly as there are lots of variables
to deal with
Repeated measures- participants do experiment in both conditions
No individual differences as the same person is used in each condition
Order effects- participants performance in each condition may improve
due to practice effects of get worse due to fatigue effects. This can be
resolved by counterbalancing (ABBA). When group A does condition A then
B and group 2 does condition B then A. Each group them repeats this but in
reverse order to balance out the order effects.
Increased chances of demand characteristics as each participant does
each condition twice which could invalidate the results.


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