experimental designs

Question 1

Experimental design

Answer 1

• how to group/organise ppt in conditions

Question 2

Types of experimental designs

Answer 2

• independent groups
• repeated measures
• matched pairs

Question 3

Definition of independent groups design

Answer 3

• ppts take part in one condition only
• each condition has different group of ppts

Question 4

How to conduct an independent groups design

Answer 4

1. group of ppts recruited
2. then split into equal sized groups
3. different group is allocated to each condition

Question 5

Strength of independent groups - AO3 - no order effects

Answer 5

• no order effects
• ppts only take part in one condition
• will not get bored/fatigue
• or better at task/have lasting effects of last condition
• (CONTEXT)
• unlike repeated measures
• where ppts take part in all conditions

Question 6

Strength of independent groups - AO3 - inappropriate

Answer 6

• used when repeated measures design inappropriate
• e.g. quasi experiment looking at gender differences
• (CONTEXT)
• each condition needs different ppts

Question 7

Limitation of independent groups - AO3 - individual differences

Answer 7

• individual differences affect DV
• as separate groups of ppts in each condition
• e.g. some ppt have better memory (CONTEXT)
• lowers internal validity
• unlike repeated measures
• uses same group in all conditions
• reduce effect of individual differences

Question 8

Limitation of independent groups - AO3 - more ppts

Answer 8

• more ppt needed
• as two different groups
• required for different conditions (CONTEXT)
• unlike repeated measures
• uses less ppts as every ppt takes part in all conditions

Question 9

Definition of repeated measures design

Answer 9

• all participants
• take part in all/both conditions
• of the experiment

Question 10

How to conduct a repeated measures design

Answer 10

1. ppts complete one condition
2. after sufficient time complete other condition
3. task (DV) should be different but match on difficulty / measure same thing

Question 11

Strength of repeated measures - AO3 - individual differences

Answer 11

• individual differences between ppt
• in each conditions removed
• e.g. IQ as confounding variables as all ppt same
• (CONTEXT)
  so researcher can be sure any changes in DV
• due to IV not any other variables
• increase internal validity
• unlike independent measures
• different ppt in different conditions
• so individual differences could affect DV

Question 12

Strength of repeated measures - AO3 - fewer ppts

Answer 12

• requires fewer ppt
• same ppts take part in all conditions (CONTEXT)
• unlike independent groups
• searate groups needed for separate conditions

Question 13

Limitation of repeated measures - AO3 - order effects

Answer 13

• order effects may occur
• ppts take part more than one condition
• may perform worse 2nd condition - boredom/fatigue
• may perform better 2nd condition - practise
• may be lasting effects from condition 1 to 2 (CONTEXT)
• lowers internal validity
• unlike independent groups
• ppts only take part one condition
• not susceptible to order effects

Question 14

Limitation of repeated measures - AO3 - demand characteristics

Answer 14

• increased chance demand characteristics
• ppts take part in all conditions
• may pick up on clues given by researcher
• spend much more time with them
• change their natural behaviour
• help or hinder research (CONTEXT)
• lowers internal validity
• unlike independent groups design
• ppts less likely pick up on clues
• only take part in one condition

Question 15

Definition of matched pairs design

Answer 15

• ppts matched on important characteristics
• e.g. age or IQ
• by giving them appropriate test
• match two ppt with same score
• each member of pair randomly allocated
• across each condition

Question 16

How to conduct a matched pairs design

Answer 16

1. chose variable to match ppt on
2. test ppt on variable before study
3. match ppt with same score
4. randomly allocate each member of pair to one condition

Question 17

Strength of matched pairs - AO3 - less individual differences

Answer 17

• reduces individual differences between ppts
• matches ppts on important variables (CONTEXT)
• so researcher can be sure any changes in DV
• due to IV not any other variables
• unlike independent measures
• separate ppt in separate conditions

Question 18

Strength of matched pairs - AO3 - no order effects

Answer 18

• no order effects
• ppt only take part in one condition
• not get bored/fatigue or better/lasting effects
• (CONTEXT)
• unlike repeated measures
• ppts take part all conditions could have order effects

Question 19

Limitation of matched pairs - AO3 - time consuming

Answer 19

• very time consuming
• to match up and find similar ppts (CONTEXT)
• especially if pre-test needed to match ppts
• on certain characteristics
• need a very large pool of people
• unlike repeated measures
• use same ppt in all conditions

Question 20

Limitation of matched pairs - AO3 - individual differences

Answer 20

• individual differences not fully eliminated
• match ppts on variables important to research
• not able to match ppts on all variables (CONTEXT)
• so questions validity of matched pairs
• unlike repeated measures
• use same ppt in all conditions
• so individual differences eliminated