PY4 - EXPERIMENTAL DESIGN

Question 1

What is an experimental design?

Answer 1

The way that two levels of the independent variable are delivered is called the experimental design

Question 2

What are the types of experimental designs?

Answer 2

• Repeated Measures
• Independent Groups
• Matched Pairs

Question 3

What is Repeated Measures?

Answer 3

All participants receive all levels of the independent variable, meaning all participants take part in all conditions of the experiment

Question 4

What are the strengths of Repeated Measures?

Answer 4

• As the same participants are used in each condition, participant variables (individual differences) are reduced.
• Fewer people are needed as they take part in all conditions (saves time).

Question 5

What are the weaknesses of Repeated Measures?

Answer 5

• There may be order effects as the order of the conditions may affect the participants behaviour. For example, performance on the second condition may be better because of a practice effect as they now have a better understanding of what is required of them. In some situations, the performance might be worse in the second condition because of boredom effect where the participant becomes bored with doing the same condition again.

Question 6

What is a method of dealing with the weaknesses of Repeated Measures?

Answer 6

• The main way that order effects are dealt with is use of counterbalancing
• Counterbalancing ensures that each condition in a repeated measures design is tested first or second in equal amounts by alternating the order in which participants perform in different conditions of an experiment.

Question 7

What is Independent Groups?

Answer 7

Participants are placed in separate (independent) groups - each group does one level of the independent variable

Question 8

What are the strengths of Independent Groups?

Answer 8

• Avoids order effects (practice or boredom) as the participants only participate in one condition.

Question 9

What are the weaknesses of Independent Groups?

Answer 9

• The researcher cannot control the effects of participant variables ( e.g. the different abilities or characteristics of each participant) - These could act as confounding variables.
• Independent groups need more participants than repeated measures design in order to end up with the same amount of data.

Question 10

What is a method of dealing with the weaknesses of Independent Groups?

Answer 10

• Randomly allocate participants to conditions which (theoretically) should distribute participant variables evenly - allocating participants to experimental groups or conditions using random techniques ( e.g. the lottery methods or random number generator)

Question 11

What is Matched Pairs?

Answer 11

There are two groups of participants who are matched on key characteristics believed to affect performance on the dependent variable
One member of each pair is allocated to Group A and to other to Group B

Question 12

What are the strengths of Matched Pairs?

Answer 12

• Reduces participant variables because the researcher has tried to pair up the participants so that each condition has people with similar abilities and characteristics.
• Avoids order effects, and so counterbalancing is not necessary.

Question 13

What are the weaknesses of Matched Pairs?

Answer 13

• It is very time consuming and difficult to match participants on key variables. The researcher will likely have to start with a large group of participants to ensure they can obtain matched pairs on key variables.
• It is not possible to control all participant variables because you can only match on variables known to be relevant, but it could be that others are important

Question 14

What is a method of dealing with the weaknesses of Matched Pairs?

Answer 14

• Restrict the number of variables to match on to make it easier
• Conduct a pilot study to consider key variables that might be important when matching