7 - Experimental Designs

Question 1

Define experimental design

Answer 1

How the participants are organised e.g. independent groups, repeated measures, matched pairs.

Question 2

Describe independent groups

Answer 2

Different participants are used in each of the conditions, therefore each group of participants is independent from one another.

Participants are usually randomly allocated to each condition to balance out any individual differences.

Question 3

Evaluate independent groups

Answer 3

+ No order effects as there are different participants in each condition.
+ Reduced demand characteristics as participants only do one condition so its harder to guess/figure out purpose of study.
+ Saves time as both participants can be tested at the same time.

• More participants needed
• Individual differences may be cause of different results rather than manipulation of IV

Question 4

Describe repeated measures

Answer 4

Each participant is tested in all conditions of the experiment

Question 5

Evaluate repeated measures

Answer 5

+ No individual differences as same people measured in all conditions
+ Half as many participants needed compared to independent groups

• Order effects may affect results. Counterbalancing can avoid this which is when half the participants do condition A first and B second and vice versa.
• Demand characteristics are more likely as they are involved in the entire study.
• Takes more time, especially if a time gap between different conditions is needed.

Question 6

Describe matched pairs

Answer 6

Participants in the two groups are matched closely on characteristics that are important for that study such as age, gender, level of education etc ( so identical twins are often used).

Question 7

Evaluate matched pairs

Answer 7

+ less risk of order effects
+ less risk of demand characteristics
+ individual differences unlikely as they are closely matched

• twice as many participants are required compared with repeated measures
• process is very difficult; even two closely matched individuals have different levels of motivation and fatigue at any given time.
• process is very time consuming

Question 8

Define order effects

Answer 8

When the sequence in which participants take part in conditions influences their performance or behaviour. For example, in memory tests participants may improve with practice. They may also get bored when asked to do more than one condition.