2.2.5 - experimental and research designs Flashcards
what are the three types of experimental design?
independent groups, repeated measures, matched pairs
what is an experimental design?
how you have organised the conditions in an experiment
how does an independent groups design work?
there is a separate group of participants for each condition of the experiment
how does a repeated measures design work?
a single group of participants take part in all the conditions of the experiment
how does a matched pairs design work?
different groups of participants are assigned to each condition of the experiment, but these groups are matched on characteristics important to the study (once matched, participants are randomly assigned to a condition)
what are the strengths of an independent groups design?
pps are less likely to guess the aim of the investigation as they don’t know about the other conditions - reduced chance of demand characteristics
it is easier to keep the conditions the same
what are the strengths of a repeated measures design?
pps are the same in all conditions so individual differences have no effect on the results between conditions
fewer participants are needed so it is more economical
what are the strengths of a matched pairs design?
it allows the conditions to be compared reliably so causation can be established (if the DV changes when the IV does, this is more likely to be due the effect of the IV, and not the differences between pps in each condition)
what are the weaknesses of an independent groups design?
twice as many pps must be recruited which could be more time-consuming and expensive
there will be individual differences between pps in each condition - they will act as confounding variables and make a comparison of the conditions unreliable (if DV changes when IV does, you don’t know whether it is because of the effect of the IV or due to the differences in pps in each condition)
what are the weaknesses of a repeated measures design?
demand characteristics are more likely - pps know about all conditions of the experiment so could guess the aim
the confounding variable of order effects becomes present - the performance of pps in one condition could be influenced by the previous condition
what are the weaknesses of a matched pairs design?
it can be difficult and time-consuming to obtain two well-matched samples
there is no guarantee that pps will be matched on all the characteristics which could affect the dependent variable
samples are generally smaller - you may lose some of the original participants if you can’t match them, and if one participant drops out you will lose their matched pair as well
