Experimental design Flashcards
What are the 3 experimental designs?
1) Repeated measures design
2) Independent groups design
3) Matched pairs design
What is meant by a repeated measures design?
Where all participants take part in all experimental conditions
What are 2 strengths of repeated measures design?
1) Good control over participant variables as the same person is tested twice (participant A may be in a better mood than participant B)
2) Fewer partcipants are needed which saves time and money
What are two weaknesses of repeated measures design?
1) Order affects are produced as the participant may be better on the second test as they get better with experience or worse due to boredom / exhaustion
2) Participants may guess the aim as they do both conditions which may make it obvious
What is meant by an independent groups design?
Each participant is allocated to a group randomly and only take part in one experimental condition
What are two strengths of independent groups design?
1) Avoids order effects as each participant is only tested once
2) Avoids participants guessing the aims of the experiment
What are 2 weaknesses of independent groups design?
1) No control over participant variables which can affect the DV (e.g ppts in group A may be more intelligent than group B)
2) More participants needed which is difficult and expensive
What is meant by a matched pairs design?
Each participant will be paired with someone who is similar, one will be placed in group A and the other will be placed in group B
What are 2 strengths of matched pairs design?
1) Control over participant variables
2) Avoids order effects
What are 2 weaknesses of matched pairs design?
1) Time consuming to match participants on key variables
2) May not control all participant variables as you can only match on variables known to be relevant and other variables may be important
What are order effects?
Where participants perform better or worse in different conditions due to familiarity with the test, boredom or exhaustion
What is meant by fatigue effects?
The performace of participants goes down throughout the experiement due to boredom / exhaustion
What is meant by practice effects?
The performance of the participants goes up throughout the experiment due to becoming familiar with the test
How can we control order effects when using a repeated measures design?
By using counterbalancing
What is meant by ‘counterbalancing’?
Half of the participants will do condition A first and the other half will do condition B first
Both groups will benefit from practice effects and so will cancel out
