experimental designs Flashcards
definition of experimental design
the different ways in which pps can be organised in relation to the experimental conditions
random allocation
an attempt to control for pp variables in an independent groups design which ensures that each pp has the same chance of being in one condition as any other
counterbalancing
an attempt to control for the effects of order in a repeated measures design: half the pps experience the conditions in one order, the other half in the opposite order
independent groups
when 2 separate groups of pps experience two different conditions of the experiment
performance of the two groups would then be compared
strength of independent groups
order effects are not a problem
limitations of independent groups
pps who occupy the different groups are not the same in terms of pp variables, random allocation
less economical bc each pp contributes to only a single result, meaning more pps are needed
repeated measures
all pps experience both conditions of the experiment
the two results from both conditions would be compared to see if there was a difference
strength of repeated measures
pp variables are controllled (higher validity)
fewer pps are needed (more economical)
limitations of repeated measures
each pp has to do at least 2 tasks and the order of the tasks may be significant, counterbalancing
order effects and demand characteristics may also arise
matched pairs
pps are paired together on a variable relevant to the experiment
one member of the pair is assigned to condition A and the other to condition
strength of matched pairs
pps only take part in one part of the condition so order effects and demand characteristics are less likely
limitations of matched pairs
matching may be time-consuming anf expensive, particularly if a pre-test is required
