Experimental Design

Question 1

what are the types of experimental design

Answer 1

• independent groups
• repeated measures
• matched pairs

Question 2

describe independent groups? Example

Answer 2

Two separate groups of participants experience two different conditions.

For example, in an experiment on talkativeness and energy drinks: one group drinks the energy drink (condition A), the other group drinks water (condition B) . We would
then compare the difference in the number of words spoken a minute for each group.

Question 3

advantages of independent groups

Answer 3

No Order effects – so participants are less likely to guess the aim

Question 4

disadvantages of independent groups

Answer 4

• Participants variables may impact experiment i.e. confidence
• Less economical (twice as many participants)

Question 5

What is repeated measures? Example

Answer 5

All participants experience both conditions.

• For example, in an experiment on talkativeness and energy drinks: each participant would first experience condition A (drinking the energy drink) and then their talkativeness will be measured. They will later experience condition B (drinking the water) and their talkativeness would be measured. Then these two scores would be compared.

Question 6

strength of repeated measures

Answer 6

• Participant variables are controlled (same person doing both conditions) =higher validity
• Fewer participants required

Question 7

weaknesses of repeated measures

Answer 7

• Order effects (fatigue, boredom, practice)
• More likely to work out aim leading to demand characteristics

Question 8

describe matched pairs? Example

Answer 8

The same as independent groups (two separate groups of participants experience two different conditions. But participants are also paired together on a variable relevant to the experiment.

• For instance, in the energy drinks experiment, we might match participants on confidence. The two most confident would be paired together and allocated to different conditions, as would the third and fourth highest, and so on.

Question 9

strength of matched pairs

Answer 9

Order effects are not a problem (participants take part in only one condition)

Question 10

weaknesses of matched pairs

Answer 10

• Participants can never be matched exactly
• Matching is time-consuming and expensive

Question 11

what is counterbalancing in repeated measures?

Answer 11

Counterbalancing is an attempt to control order effects in a repeated measures design. In counterbalancing, half the participants take part in condition A and then B and then half take part in condition B then in A