Experimental design

Question 1

What is a repeated measure design?

Answer 1

Each ppts takes part in every condition being tested.
Each condition represents one level on the independent variable (IV).
There may be a control condition

Question 2

What are some strengths about a repeated measures design?

Answer 2

• Good control of ppt variables because the same person is tested twice. In an independent groups design the people in group A may be happier and thats why they do better on a tast than group B. In a repeated measures design such ppt vairables are the same across conditions
• Fewer ppts are need than with independent group design because, if you have 20 ppts you end up with 20 rather than 10 results in the final analysis. This is important because more data makes the conclusion more dependable.

Question 3

What are some weaknesses in repeated measures design?

Answer 3

• Order effects are produced, for example a ppt may be better on the second test because of getting better with experience (a practice effect) or may perform less well because of being bored or tired (fatigue effect)
• Ppts may guess the purpose of the experiment because they do both conditions and this mat make the research aim obvious

Question 4

How may we deal with the weakness of repeated measures design?

Answer 4

Can control order effects with counterbalancing- which is ABBA

Question 5

What are independent groups design?

Answer 5

Different ppts are allocated to 2 or more experimental groups representing different levels of the independent variable. There may be a control group

Question 6

What are some strength of independent groups design?

Answer 6

• Avoids order effects because each ppts is only tested once
• Avoids ppts guessing the aims of the experiment

Question 7

What are some weaknesses of independent groups design?

Answer 7

• There is no control of ppt variables
• Needs more ppts than with a repeated measures design

Question 8

How could we deal with the weaknesses of an independent groups design?

Answer 8

Lack of control over ppts cariables can be dealt with by using randomisation of ppts to conditions. This means ppts variables should not cluster in one particular group

Question 9

What is matched pairs design?

Answer 9

Ppts who are similar on key variables are paired. One member of the paur is places in group A and the other in group B.
This means there are 2 groups of ppts. Each group is given one level of independent variable.

Question 10

What is a strenght of using a matched pairs design?

Answer 10

• Controls for ppt variables because of the matching (means that it is similar to repeated measures)
• Avoids order effects because it is like an independent groups design

Question 11

What is a weakness of using a matched pairs design?

Answer 11

• Very time consuming to match ppt on key variables
• May not control all ppt variables because you can only match on variables known to be relevant, but it could be that other variables are important

Question 12

How could we deal with the weakness of using a matched pairs design?

Answer 12

YOu should start with a large group of ppt to ensure you can obtain matched pairs on key variable