methods: experimental design Flashcards
(18 cards)
what is repeated measures design?
- same ppts used in all experimental conditions
- they do all the conditions
what are the advantages of a repeated measures design?
- controls individual differences
- same people do all conditions
- results are compared within each person
- needs fewer ppts
- more economical than independent groups
what is a disadvantage of repeated measures design? (dc)
- higher chance of demand characteristics
- ppts see all conditions
- more likely to guess the aim of the study
what is a disadvantage of repeated measures design? (oe)
- order effects
- performance is influenced by doing another condition first
- includes practice (get better) and fatigue (get worse)
- can affect results in the second condition
what is one way of controlling demand characteristics? (repeated)
- use single blind technique
how can order effects be controlled in repeated measures design?
- use randomisation or counterbalancing
- ppts do conditions in different orders
- helps reduce practice and fatigue effects
what is randomisation in repeated measures design?
- selecting at random which condition ppts do first
- can be done by picking a card out of a hat
what is counterbalancing and the ABBA design in repeated measures?
- counterbalancing: ppts do conditions in different orders (AB or BA)
- controls for order effects (practice or fatigue)
- ABBA design: participants do conditions twice (A, B, B, A)
- mean score for both conditions is taken to balance order effects
what is a Latin square in repeated measures design?
- used when there are more than two conditions
- designates ppts to different combinations of ordering
- balances out order effects between groups
- ensures each condition appears in each position
how can time gaps help reduce order effects in repeated measures design?
- leave a time gap between conditions A and B
- reduces fatigue effects
- may not reduce practice effects, depending on the task
what is an independent groups design?
- only one experimental condition tested on each group of ppts
- different ppts in each condition
what is a strength of the independent groups design?
- ppts only take part in one condition
- less likely to guess the aim of the study
- reduces demand characteristics and expectancy effects
what is a disadvantage of the independent groups design?
- requires twice as many ppts
- separate groups for each condition
- individual differences may make group comparisons unreliable
how can individual differences be controlled in an independent groups design?
- use random allocation
- gives ppts an equal chance of being in any condition
- helps ensure an even distribution of ppt variation
what is a matched pairs design?
- similar to independent groups but ppts are matched on key characteristic
- different ppts in each condition
- helps control individual differences like a repeated measures design
what is important when matching participants in a matched pairs design?
- match ppts on characteristics central to study
- for example, match on driving experience or reaction time in a driving study
- avoid matching on irrelevant traits like hair colour
what is a strength of the matched pairs design?
- ensures more reliable comparison between conditions
- differences between conditions are more likely due to the manipulated variable
- helps establish causation
what is a disadvantage of the matched pairs design?
-
time-consuming to match ppts
- many may be excluded for not meeting matching criteria
- difficult to match on all possible relevant variables
- some variables (e.g. parental education) are hard to control
