Experimental Designs

Question 1

What is an experimental design?

Answer 1

The experiments, design of a study is how participants are assigned to different conditions

Question 2

What are the three main types of experimental designs?

Answer 2

• independent groups
• repeated measures
• matched pairs

Question 3

What is the independent groups design?

Answer 3

In the independent groups design, different parts are used in each of the conditions = each group is independent from one another —> part susially randomly allocated to each condition to balance out any participant variables

Question 4

What are the ads of independent groups?

Answer 4

1) Order effects will not occur as there are different participants in each condition Order effects are when the sequence in which participants take part in conditions influences their performance or behaviour. E.g., in a memory test participants may get better with practice. Participants may also get tired or bored or fatigued whenbeing asked to take part in more than one condition.
2) The chance of demand characteristics is reduced as participants do only one conditioneach and so have less chance to guess the purpose of the study.
3) As both groups of participants can be tested at the same time this experimental design saves time

Question 5

What are the disads of independent groups?

Answer 5

1) More participants are needed for this experimental design = can’t reuse previous parts
2) There is always a chance that the different results between the two conditions are due to participant variables rather than manipulation of the independent variable (IV)

Question 6

What is the repeated measures design?

Answer 6

In the repeated measures design, each participant is tested in all conditions of the experiemnt

Question 7

What are the ads of repeated measures?

Answer 7

1) as same ppl are measured in a lil conditions, there are no participant variables between the conditions
2) half as many participants are needed compared to an independent groups design

Question 8

What are the disads of repeated measures?

Answer 8

1) Order effects may affect the results. One way to avoid this is counterbalancing, this is when half the participants do condition A first and condition B second and the other half of the participants do condition B first and condition A second. Counterbalancing does not eliminate order effects, which will be present because there are two separate tasks to be completed by each person. However, counterbalancing controls the impact of order effects (practice, fatigue or boredom) and allows order effects to be distributed evenly across both conditions
2) demand characteristics are more likely to occur as participants are involved in the entire study
3) the experimental design takes more time, especially if a time gap between different conditions is required

Question 9

What is the matched pairs design?

Answer 9

In the matched pairs design, different parts are used in all the conditions, same as independent groups design

However mowers in the two groups are matched on characteristics important for the study e.g. age, gender, level of education etc.. identical twins are often used in matched pairs designs

Question 10

What are the ads of matched pairs?

Answer 10

1) less risk of order of effects
2) there is less risk of demand characteristics
3) participant variables are unlikely as the groups have been closely matched

Question 11

What are the disads for matched pairs?

Answer 11

1) twice as many parts are required compared with a repeated measures design
2) the matching process is incredibly difficult = even two closely matches individuals have different levels of motivation + fatigue at any given time
3) matching process is incredibly time consuming