psych (science skills)

random sampling

selecting participants from the population randomly so that each member of the population has an equal chance of being selected

stratified sampling

dividing the population into subgroups, then randomly selecting participants from each subgroup

qualitative data

data that is characterised and catogorised

quantitative data

data that can be measured numerically

within subjects design

all participants in the sample being involved in both experimental and control conditions

between subjects design

participants are randomly allocated to either control or experimental conditions

mixed design

combines between subjects and within subject designs

disadvantage of between subjects design

time consuming as groups had to be tested at separate times

disadvantage of within subjects design

practice effect - prior participation in the first condition may influence their behaviour while completing the second condition

advantage of within subjects design

no participant variables between groups, improving validity

advantage of between subjects design

lower rate of participant withdrawal because participants only complete one condition