4.2.3.1 EXPERIMENTAL DESIGN

Question 1

what does experimental design show?

Answer 1

how the ppt sample is used in combination with the different levels of the IV

Question 2

there are three main types of experimental design

what are these?

Answer 2

1) repeated measures

2) independent groups

3) matched pairs

Question 3

what is the independent groups / independent measures design?

Answer 3

• different ppts take part in each condition of the IV
• each condition of the experiment includes a different group of ppts
• each set of ppts only experience one condition of the IV
• ppts are randomly allocated to each condition
  -> avoids researcher bias
  -> ensures each ppt has an equal chance of being assigned
• involve using two separate groups of ppts
• produces unrelated data

Question 4

what are 3 strengths of independent measures design?

Answer 4

1) avoids order effects
-> ppl participate in one condition only
-> things like practise or fatigue

2) time efficient
-> all sets of ppts can be tested at the same time

3) less likely to have demand characteristics
-> ppts only take part in 1 condition
-> less likely to guess the purpose/how to behave

Question 5

what are 2 limitations of independent measures design?

Answer 5

1) ppt variables
-> if more ppts with a particular characteristic are all assigned randomly to 1 condition, can affect the measure of the IV
-> eg) age, gender, social background

2) more people needed than the repeated measures design
- more time consuming
- can be difficult to access

Question 6

what is the matched pairs design?

Answer 6

• different but similar ppts are used in each condition
• matched on variables relevant to the study
• monozygotic twins can be good for this as they’re genetically perfectly matched
  -> 100% the same, come from 1 zygote
• one member of each pair is placed into the experimental group and the other member into the control group
  -> via random allocation
• produces related data

Question 7

what are 2 strengths of matched pairs?

Answer 7

1) reduces ppt variables
- because the researcher has tried to pair up the ppt so that each condition has people with similar abilities and characteristics

2) avoids order effects
- so counterbalancing isn’t necessary
- ppts only take part in 1 condition

Question 8

what are 3 weaknesses of matched pairs?

Answer 8

1) very time-consuming trying to find closely matched pairs

2) impossible to match people unless identical twins

3) more ppts needed to ensure there are enough to take part in the different conditions
-> can be difficult to access

Question 9

what is the repeated measures design?

Answer 9

• every ppt takes part in every condition
  -> the same ppts take part in each condition of the IV
• each condition of the experiment includes the same group of ppts
• the results are compared to themselves
• produces related data

Question 10

what are 2 strengths of repeated measures?

Answer 10

1) the same ppts are used in each condition
- ppt variables are reduced
- no group differences

2) fewer people are needed
- they take part in all conditions and produce more data per ppt

Question 11

what are 3 limitations of repeated measures?

Answer 11

1) may be order effects
- ppts may guess aims and change their behaviour (demand characteristics)
- this can be controlled by counterbalancing though

2) demand characteristics
- more likely as ppts are more likely to guess the purpose of the research due to taking part in multiple conditions

3) more time usually needed
- to allow for the ppts to take part in multiple conditions

Question 12

what is counterbalancing?

Answer 12

• the sample would split up into two groups
• experimental (A)
• control (B)

eg) group 1 does A then B
group 2 does B then A

• this should eliminate order effects