experimental designs

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Experimental designs
Repeated measures
Participants repeat the experiment in each condition
Example- condition 1- listening to music whilst learning a list of pictures,
condition 2- learning a list of pictures in silence. Each participant will take
part in both conditions
Strengths Weaknesses
Reduces number of individual It can produce the extraneous variable
differences as the same people are used of practice and fatigue effects. To
in each condition. This removes a overcome this counter balancing can be
possible confounding variable, used.
improving the internal validity of the
conclusions
Counter balancing is when half of the participants do condition A first then
condition B, the other half do condition B first then condition A. This
balances the practice and fatigue effects
Independent samples
Different participants in each condition
Strengths Weaknesses
Removes possible extraneous variables Introduce a different extraneous
of practice and fatigue effects, and variable of individual differences so
reduces the likelihood of demand for example boys may be better as
characteristics as the participants only they have better memory than girls
take part in the study once and so are
less likely to determine the hypothesis
Matched pairs
The sample are matched into pairs depending on characteristics, similar ages,
similar IQ or personality
Strengths Weaknesses
Reduced possibility of individual Hard to match pairs accurately and
differences becoming a confounding almost impossible to match participants
variable, avoids practice and fatigue on all types of variable, which can
effects and reduces chance of demand affect the performance of the
characteristics experiment

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