L7 - Experimental Designs

Question 1

What is the experimental design of a study?

Answer 1

• It’s how participants are assigned to different conditions.
• There are three main types of experimental designs, independent groups, repeated measures, and matched pairs.

Question 2

What is the independent groups design?

Answer 2

• This is where different participants are used in each of the conditions.
• Therefore, each group of participants is independent from one another.
• Participants are randomly allocated to each condition.

Question 3

Advantages of Independent Groups

Answer 3

1. Order effects will not occur as there are different participants in each condition.
2. The chance of demand characteristics is reduced as participants only do one condition each and so have less chance to guess the purpose of the study.
3. As both groups can be tested at the same time, this design saves time.

Question 4

Disadvantages of Independent Groups

Answer 4

1. More participants are needed for this design
2. There is always a chance that different results between the 2 conditions are due to participant variables rather than manipulation of the IV.

Question 5

What are repeated measures?

Answer 5

This is when each participant is tested in all conditions of the experiment

Question 6

Advantages of Repeated Measures

Answer 6

1. As the same people are measured in all conditions there are no participant variables.
2. Half as many participants are needed compared to the independent groups design

Question 7

Disadvantages of Repeated Measures

Answer 7

1. Order effects may affect the results. However, counterbalancing can control the impact of counterbalancing, but it does not eliminate it entirely.
2. Demand characteristics are more likely yo occur as participants are involved in the entire study.
3. This design takes more time, especially if a time gap between conditions is required.

Question 8

What are matched pairs?

Answer 8

• Different participants are used in all of the conditions, like Independent group design.
• However, participants in the 2 groups are matched on characteristics important for that study, such as age or gender.
• Identical twins are often used in matched pairs design

Question 9

Advantages of matched pairs

Answer 9

1. There is less risk of order effects
2. There is less rick of demand characteristics
3. Chances of participant variables are unlikely as individuals have been closely matched.

Question 10

Disadvantages of matched pairs

Answer 10

1. Twice as many participants are required, compared to repeated measures design.
2. The matching process is extremely time consuming.
3. The matching process is also. very difficult, as even two closely matched individuals may have different levels of motivation or fatigue.