Experimental Designs

Question 1

What is a repeated measures design?

Answer 1

Participants experience all conditions of the experiment.

Often takes place in the form of participants being tested before and after the manipulation of the IV.

Question 2

What are the strengths of a repeated measures design?

Answer 2

Controls participant variables because the same participants take part in both conditions. This reduces the chance of the extraneous variable affecting the DV.

Question 3

What are the weaknesses of a repeated measures design?

Answer 3

1. Participants have more opportunity to guess the aim of the study as they do both conditions. Increases possibility of demand characteristics which will cause unnatural behaviour and effect the validity of the study.
2. Order effects - participant’s performance in the second condition may be affected by their performance in the first (e.g fatigue, boredom, practice)

Question 4

What is an independent groups design?

Answer 4

Involves using different participants in each condition of the study. Participants are (where possible) randomly assigned to a group.

Question 5

What are the strengths of an independent groups design?

Answer 5

1. Less chance of demand characteristics compared to a repeated measures design as they’re only aware of one condition so are less likely to guess the aim of the study.
2. No order effects as they only take part in one condition unlike the repeated measures design.

Question 6

What are the weaknesses of an independent groups design?

Answer 6

May be individual differences (participant variables) between the two groups before the study which you would not get in a repeated measures design. May be responsible for differences in behaviour.

(e.g better memory, more sleep, caffeine)

Question 7

What is a matched pairs design?

Answer 7

Involves using different participants for each condition but matching them up first on a variable import to the control in the study.

Matched into pairs based on similar performance from a pre-tested variable.

Question 8

What are the strengths of a matched pairs design?

Answer 8

1. Eliminates the order and practice effects of a repeated measures design (order effects) as they only take part in one condition.
2. Reduces individual differences (participant variables) between participants as they are matched with someone with similar contributing attributes.

Question 9

What are the weaknesses of a matched pairs design?

Answer 9

1. May be impractical as it’s time consuming and difficult to match up participants on specific variables.
2. Impossible to match participants on every variable that could possibly effect results.