Experimental designs

Question 1

Independent groups

Answer 1

One group does condition A and a second group does condition B

Participants should be randomly allocated to experimental groups

Question 2

3 experimental designs

Answer 2

Independent groups
Repeated measures
Matched pairs

Question 3

2 advantages of independent groups + explain

Answer 3

No order effects - participants are only tested once so can’t practise or become bored/tired. This controls an important CV

Will not guess aim - participants only tested once so are unlikely to guess the research aims. Therefore behaviour may be more ‘natural’ (higher realism)

Question 4

2 disadvantages of independent group + explain

Answer 4

Participant variables - the participants in the two groups are different, acting as EV/CV. May reduce the validity of the study.

Less economical - need twice as many participants as repeated measures for the same data. More time spent recruiting which is expensive

Question 5

Repeated measures

Answer 5

Same participants take part in all conditions of an experiment.

The order of conditions should be counterbalanced to avoid order effects

Question 6

2 advantages of repeated measures + explain

Answer 6

Participant variables - The person in both conditions has the same characteristics. This controls an important

Fewer participants - Half the number of participants is needed than in independent groups. Less time is spent recruiting

Question 7

2 disadvantages of repeated measures + explain

Answer 7

Order effects are a problem - participants may be doing better or worse when doing a similar task twice. Also practice/fatigue effects. Reduces the validity of the results

Participants guess aims - participants may change their behaviour. This may reduce the validity of the results

Question 8

Matched pairs

Answer 8

Two groups of participants are used but they are also related to each other by being paired on participant variables that matter for the experiment

Question 9

2 advantages of matched pairs + explain

Answer 9

Participant variables - participants matched on a variable that is relevant to the experiment. This controls participant variables and enhances the validity of results

No order effects - participants are only tested once so no practice or fatigue effects. This enhances the validity of the results

Question 10

2 disadvantages of matches pairs + explain

Answer 10

Matching is not perfect - it is time consuming and can’t control all relevant variables. Cannot address all participant variables

More participants - need twice as many participants as repeated measures for same data. More time spent recruiting which is expensive