research methods: experimental designs

Question 1

What does experimental design mean?

Answer 1

The arrangement of groups of participants in an experiment

Question 2

What are the three types of experimental design?

Answer 2

• repeated measures
• independent groups
• matched pairs

Question 3

What is the repeated measures design?

Answer 3

All participants take part in all the conditions of the experiment

Question 4

What kind of data is produced from the repeated measures design?

Answer 4

Produces related data as each pps score in one condition can be paired with a data point in the other condition

Question 5

Evaluation of repeated measures: order effects -> limitation

Answer 5

• Taking part in the first condition influences performance in the second condition
• in the second condition, they may do better e.g. due to practice or worse e.g. due to tiredness or boredom
• therefore, it is unclear whether the change in the second condition was due to improvement or the experimental IV
• Order acts as a confounding variable

Question 6

Evaluation of repeated measures design: demand characteristics -> limitation

Answer 6

Participants are also more likely to work out the aim of the experiment when they experience all the conditions of the experiment

Question 7

How can order effects in the repeated measures design be controlled?

Answer 7

• Through counterbalancing which uses the ABBA format
• half the participants complete condition A first and B second, the other half of the same start with condition B then A

Question 8

What is the independent groups design?

Answer 8

Different participants are used in each condition of the experiment

Question 9

How are pps allocated in the independent groups design?

Answer 9

Participants are randomly allocated to each condition to avoid researcher bias when assigning to conditions

Question 10

What kind of data does the independent groups design produce?

Answer 10

Produces unrelated data as the individual data points in one condition cannot be paired with any of the data points in the other condition

Question 11

Evaluation of the independent groups design: participant variables -> limitation

Answer 11

• The pps who occupy different groups are not the same in terms of participant variables
• If more participants with a particular characteristic are randomly assigned to one of the groups e.g. age, this can influence the measurement of the DV (an extraneous variable)
• reduces the validity of the results

Question 12

How can participant variables be dealt with?

Answer 12

Using random allocation where pps are randomly allocated to different experimental conditions
- attempts to evenly distribute participant characteristics across the conditions of the experiment using random techniques

Question 13

Evaluation of independent groups design: economical -> limitation

Answer 13

The independent groups design is less economical than the repeated measures design as each participant contributes as a single result only
- twice as many participants would be required to produce an equivalent data to that collected in a repeated measures design

Question 14

Evaluation of independent groups design: order effects -> strength

Answer 14

Order effects are not a problem as pps take place in one condition
- while they are in repeated measures as participants are more likely to guess the aims

Question 15

What are matched pairs?

Answer 15

Pairs of participants are matched in terms of key variables, such as age or socioeconomic status
- each participant only takes part in one condition

Question 16

What is the effect of having one partipant from each pair allocated to a different condition?

Answer 16

An attempt to control the confounding variables and participant variables

Question 17

What kind of data does the matched pairs design produce?

Answer 17

Related data as each pps score in one condition can be paired with a data point of their partner in the other condition

Question 18

What are the advantages of the matched pairs design (evaluation)

Answer 18

• Reduced participant variables as participants are matched on a relevant characteristic
• no order effects as participants only take part in one condition

Question 19

What are the limitations of the matched pairs design (evaluation)

Answer 19

• Takes longer to set up than other experimental designs (more time consuming)
• Needs twice as many participants as a repeated measures design (more expensive)
• Participants are similar but not identical so there may still be some participant variables between conditions that influence the dependent variable