RM- Experimental designs Flashcards
What does experimental design mean?
The experimental design of a study is how participants are organised within an experiment.
What are the main 3 types of experimental designs?
Independent groups, repeated measures and matched pairs
What is independent groups design?
- In this design different participants are used in each of the conditions.
- Therefore each group of participants are independent from each other.
How can we control the independent groups design?
- Participants are usually randomly allocated to each condition.
- E.g picking names out of the hat
What are the advantages of independent groups design?
1) Order effects won’t occur as there are different pps in each condition. Order effects is when the sequence in which pps take part in influence their performance/behaviour.
2) The chance of demand characteristics is reduced as pps take part in only one condition each and so have less chance to guess aim of study.
3) Pps not lost between trials because they only take part in one condition and then leave.
What is order effects?
When the sequence in which pps take part in influences their performance or behaviour.
What are the disadvantages of independent groups design?
1) More pps are needed for this experimental design compared to a repeated measures design.
2) There is always a chance that different results gained between the two conditions are due to individual differences rather than manipulation of the independent variable.
What is a repeated measures design?
In a repeated measures design each pp is tested in all conditions of the study.
What are the advantages of the repeated measures design?
1) As the same people are used in all of the conditions, there are no individual differences between the conditions. Therefore the study is more valid.
2) Half is many pps are needed in this design compared to an independent groups design. This is because one group of pps are used in condition 1 and condition 2.
What are the disadvantages of the repeated measures design?
1) Order effects may affect results. One way to avoid order effects is counterbalancing, this is where half the pps do condition A first then condition B second and the other half do condition B first and condition A second.
2) Demand characteristics are most likely to occur as pps are involved in the entire study and take part in two conditions therefore might guess aim of the study.
What are matched pairs design?
- In the matched pairs design, different pps are used in all the conditions just like independent groups design.
- However pps in the two groups are matched on characteristics important for the study, such as age,gender, level of education
What are the advantages of the matched pairs design?
1) Less risk of order effects as pps only take in one condition only.
2) Individual differences less likely to occur as groups have been closely matched on specific characteristics.
What are the disadvantages of the matched pairs design?
1) Twice as many pps are required compared to repeated measures design.
2) The matching process is incredibly difficult and time consuming and individual differences cannot be completely controlled and removed.
