Please enable JavaScript.
Coggle requires JavaScript to display documents.
Experimental design - Coggle Diagram
Experimental design
- independent group design = ppts allocated to different groups where each group represents one experimental condition
- if two levels of the IV are present, all ppts experience one level of the IV only
- performance of the groups will be compared
:green_cross: ppts who occupy the different groups aren't the same so if research finds a mean difference between groups on the DV this could be due to individual differences than the effects of the IV
- to deal with this problem researchers use random allocation
:green_cross: less economical than repeated measures as each ppt contributes a single result only. 2x as many ppts would be needed to produce equivalent data to that collected in repeated measures design
:check: using independent groups are that order effects aren't a problem whereas they're a problem for repeated measures design
-
:green_cross: each ppt has to do at least two tasks & order of these task may be significant (i.e. there's order effects)
- to deal with this, researchers use counterbalancing
:green_cross: Order effects also happen because repeating tasks could = boredom/fatigue = deterioration in performance on following tasks so it matters the order of the tasks
:check: ppts performance may improve through repetition, especially on skill-based tasks - ppts would perform better in future tasks. so order acts as confounding variable
:green_cross: ppts may work out aims of study when they experience all conditions of the experiment. so demand characteristics tend to be more of a feature of repeated measures design than independent groups
-
:check: ppts only take part in single condition so order effects & demand characteristics are less of a problem
:green_cross: despite attempt to reduce ppts variables in this design, ppts can never be matched identically. even when identical twins are used as matched pairs, there'll still be important difference between them which may affect the DV
:green_cross: matching may be time-consuming & expensive, especially if a pre-test is required = less economical than other designs
- repeated measures = all ppts take part in all conditions of the experiment
- two sets of data from both conditions would be compared to see if there was a difference
- this design at least guarantees that we are comparing 'like with like'
- unlike independent group design which assesses performance of two different groups of people which may be a problem
- matched pairs design = pairs of ppts are first matched of some variable(s) what may affect the DV. then one member of the pair is assigned to Condition A and the other to Condition B
- e.g. in memory study, ppts may be matched on their IQ as this may be good indicator of their ability to recall info. two ppts with 1st & 2nd highest IQ scores would be paired, as would ppts with 3rd & 4th & so on with 5th & 6th etc.
- 1 ppts from each pair would be allocated to different condition of the exp. = attempt to control for confounding variable of ppts variables & often necessitates the use of a pre-test if matching id to be effective
- main issue with repeated measures is when ppts are tested more than one & experience all conditions of exp, there is an increased likelihood they'll become wise to the aims of the study
-
- experimental design = way in which ppts are used in experiments. i.e. how the testing of ppts is arranged in relation to the different experimental conditions