Experimental designs

Question 1

Independent groups

Answer 1

1 condition A, 2nd condition B. Parts randomly allocated to experimental groups.
+ No order effects - parts only tested once so can’t practice or become tired/bored - controls important CV
+ Won’t guess aim - Parts only tested once ->behaviour may be more natural - higher realism
-Participant variables - Parts in 2 groups are different acting as EV/CV - reduce validity of study
-Less economical - Need twice as many parts as repeated measure for same data - more time spent recruiting - more expensive

Question 2

Repeated measures

Answer 2

Same participants take part in all conditions of experiment. Order of conditions should be counterbalanced to avoid order effects.
+ Participant variables - person in both condition has same characteristics - controls important CV
+ Fewer participants - Half number of participants is needed than in independent groups - less time recruiting participants
- Order effects - participants may perform better or worse when doing similar task twice. Practice/fatigue effects - Reduces validity of results
- Participants guess aims - may change behaviour - may reduce validity of results

Question 3

Matched pairs

Answer 3

2 groups of parts paired on part variables
+ Part variables - Matched on variable relevant to experiment - controls PVs and enhances validity
+ No order effects - Only tested once so no practice or fatigue effects - enhances validity
- Matching is not perfect - time-consuming, can’t control all relevant variables - can’t address all PVs
- More parts - need twice as many participants as repeated measures for same data - more time spent recruiting - expensive