Experimental Designs Flashcards
What are the three experimental designs?
Independent groups
Repeated measures
Matched pairs
What is the difference between an experimental method and experimental design?
Experimental method is how exp is carried out and experimental design is how ppts are organised within exp
What is meant by an independent groups design and how is it conducted?
- ppts only take part in one condition, each condition has diff groups of ppts
- gather group of ppts
- split into equal sized groups
- allocate each group to a diff condition
What are the strengths and weaknesses of independent groups design?
Strengths
- no order effects
Weaknesses
- indv differences
- more ppts are required
Describe the strength of no order effects for independent groups design
- no order effects as ppts only take part in one condition so they wont get bored, tired or better at task
Describe the weaknesses indv diff and more ppts required for independent groups design
- indv diff may affect DV as there are seperate groups of ppts in each condition, so in one condition ppts may have a specific trait that makes them perform better at DV, meaning IV wasnt the only thing affecting DV, red int val
- more ppts required as a diff group is needed for each condition
What is meant by a repeated measures design and how is it conducted?
- all ppts take part in all conditions of the exp
- ppts complete in one condition
- after a time gap, they will complete the other condition
- the task should be diff but matched on difficulty/measuring the same thing
What are the strengths and weaknesses of a repeated measures design?
Strengths
- no indv diff
- requires fewer ppts
Weaknesses
- order effects
- inc chance of demand characteristics
Describe the strength indv diff and requires fewer ppts for a repeated measures design
- indv diff bw ppts in each condition are removed such as ppts having a specific trait in one condition making them perform better at DV, as all ppts take part in all conditions, therefore researcher can be more sure IV had an effect on DV and other variables didnt have an effect, inc int val
- requires fewer ppts as same ppts take part in all conditions
Describe the weaknesses order effects and inc chances of demand characteristics for a repeated measures design
- order effects may occur when ppts take part in more than one condition, so they may get bored, tired or do better in next condition due to practice, lowering int val
- inc chances of demand characteristics as ppts take part in all conditions so they may pick up on clues given off by the researcher and change nat bhv to help researcher, lowering int val
What is meant by a matched pairs design and how is it conducted?
- ppts are matched on characteristics/variables important to exp e.g. age
- choose characteristic/variable to match ppts on
- test ppts on this variable before study
- match ppts with same scores
- randomly allocate each member of pair to one condition
What are the strengths and weaknesses of matched pairs design?
Strengths
- reduces indv diff
- no order effects
Weaknesses
- very time consuming
- cannot fully eliminate indv diff
Describe the strengths of indv diff and no order effects for matched pairs design
- indv diff reduced bw ppts as it matches ppts on variables important to exp e.g age, therefore researcher can be more sure that IV effects DV and not any other variables
- no order effects as ppts only take part in one condition so they wont get bored/fatigued or become better at task
Describe weaknesses that its very time consuming and indv diff cannot be fully eliminated
- very time consuming to match similar ppts esp is they need to be tested to match ppt on certain variable important to exp, psychologist will need many options of people
- indv diff cant be fully eliminated as psychologists match ppts on variables important for research but arent able to match ppts on all variables, therefore could question val of matched pairs design
