This a summary of the experimental designs which helped me consistently get A*s in A Level psychology. It is easy to comprehend and consists of the main points. These are required in methods in contexts questions and more specifically the research methods section of paper 2. It is also essential to...
Experimental Explanation Strengths Limitations
design
Independent Different participants are used in each condition of the Avoids order effects (such as More people are needed (i.e., more time
groups independent variable. practice or fatigue) as people consuming).
participate in one condition only. Differences between participants in the
groups may affect results, for example;
variations social background. These
differences are known as participant
variables (i.e., a type of extraneous variable).
Repeated The same participants take part in each condition of the As the same participants are used There may be order effects. Performance in
measures independent variable. in each condition, participant the second condition may be better because
variables (i.e., individual the participants know what to do (i.e.
differences) are reduced. practice effect); Or worse because they are
Fewer people are needed as they tired. This limitation can be controlled using
take part in all conditions (i.e. counterbalancing.
saves time).
Counterbalancing The sample would split into two groups experimental (A)
and control (B). For example, group 1 does ‘A’ then ‘B,’
group 2 does ‘B’ then ‘A’ this is to eliminate order
effects. Although order effects occur for each
participant, because they occur equally in both groups,
they balance each other out in the results.
Matched pairs An effort is made to match the participants in each Reduces participant variables Impossible to match people exactly, unless
condition in terms of any important characteristic which because the researcher has tried to identical twins!
might affect performance, e.g. intelligence. One member pair up the participants so that Very time-consuming trying to find closely
of each matched pair must be randomly assigned to the each condition has people with matched pairs.
experimental group and the other to the control group. similar abilities and characteristics.
Avoids order effects.
Experimental design refers to how participants are allocated to the different conditions (or IV levels) in an experiment.
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