Experimental Designs

What is the repeated measures design?

The same participants are used in all conditions of the IV.

What are the strengths of the repeated measures design? (2)

• Individual differences are eliminated therefore any difference between their performance in each level of the IV should be to the experimenter’s manipulation.

• Fewer participants required

What are the limitations of the repeated measures design? (3)

• Order effects such as practice, boredom or fatigue may occur, although these can be evenly distributed across conditions by counterbalancing

• Demand characteristics: because participants take part in all conditions

• It is sometimes not possible to use the same material in each condition

What is the independent groups design?

Participants are placed in separate groups. Each group does one level of the independent variable.

What are the strengths of the independent groups design? (3)

• No order effects: participants are only involved in one condition

• There is less opportunity to become aware of the aim reducing demand characteristics

• The same material can be used in both conditions

What are the limitations of the independent groups design? (2)

• Participant variables are introduced. Differences between the conditions mar be caused by the different people rather than the independent variable.

• More participants are required

What is the matched pairs design?

Pairs of participants are closely matched in a relevant characteristic (e.g. age, gender etc.) Each participant in the pair is randomly allocated to one condition or the other.

What are the strengths of the matched pairs design? (4)

• Avoids order effects

• Avoids demand characteristics

• Reduces individual differences

• The same material can be used in both conditions

What are the limitations of matched pairs design? (2)

• It is difficult to match everything about the participants

• It is very time consuming and requires more participants