Chapter 9: Within group design Flashcards
Within group design
Only one treatment group
Each participant is given all levels of the IV
Comparison is made between scores obtained at different levels of the IV for the same participant
Types of within group design (2)
1) Concurrent measures
2) Repeated measures
Concurrent measures
All levels of IV are present at the same time (choice paradigm)
Simplest case scenario: subjects choose the value of IV they prefer
Repeated measures
Every participant receives all levels of IV (one after the other), and the participant’s results are the basis for comparison
1) Equates groups by using the same participants
2) Reduces within group variance by controlling for individual differences
Carryover effects
Major problem in within-group designs
Effects that one treatment may have on another treatment
Exposure to one manipulation may produce persistent consequences influencing the participants response on the subsequent manipulations
Complete counterbalancing
All possible treatment orders are used equally
Partial counterbalancing (Latin Square)
Each treatment occurs equally often in each position in the experiment
Irreversible carryover effects
Effects of the IV that permanently alter the development/state of participants
Reversal design (ABA design)
Verify presence of carryover effects
A: measure behaviour at baseline
B: measure during intervention
A: measure after intervention stopped
What does it mean when behaviour returns to baseline in an ABA design?
It means there is no carryover effects
Advantages of within-group design (4)
1) Fewer participants needed
2) Greater sensitivity to treatment effect due to elimination of variance caused by individual differences
3) Each participant acts as his own control
4) Very powerful design under suitable conditions
Disadvantages of within-group design (2)
1) Carryover effects
2) Participant attrition may be a problem
