R: 9/10 Flashcards
Carryover effects
Changes in behaviour that are caused by the lingering aftereffects of an earlier treatment condition. Carryover effects exist whenever one treatment condition produces a change in the participants that affects their scores in subsequent treatment conditions. Eg a drug or contrast effect
Threats to internal validity for within-subjects design
Confounding from environmental variables
- morning/afternoon
- different rooms
Confounding from time-related factors
- history
- maturation
- instrumentation
- testing effects
- statistical regression
Progressive error
Refers to changes in a participants behaviour that are related to general experience in a research study but not related to a specific treatment. E.g. practice effects or fatigue
How can you control environmental threats to internal validity?
- Randomisation
- Holding them constant
- Matching across treatment conditions
Limitations to counterbalancing
- does not eliminate order effects, just evenly distributes them across the treatment conditions, though not usually a problem because researchers are typically interested in the amount of diff b/w treatments not the absolute magnitude of specific mean
- adds the order effects to some individuals within each treatment but not to all
- order effects may not be symmetrical
- partial counterbalancing uses enough different orderings to ensure that each treatment condition occurs first in the sequence for one group, second for another via a Latin square.
Differences between within-subjects and between-subjects design
- individual differences
- time-related and order effects
- number of participants
Matched-subject design
Each individual in one group is matched with a participant in each of the other groups. Is done so that the matched individuals are equivalent with respect to a variable that the researcher considers relevant to the study
