within-subjects experimental design OR
repeated-measures experimental design
compares two or more different treatment conditions by observing or measuring the same group of individuals in all of the treatment conditions being compares
- Confounding from environmental variables
from time-related variables
threats to internal validity to Within-subjects experiments
defined as changing the order in which treatment conditions are administered from one participant to another so that the treatment conditions are matched with respect to time.
threat to internal validity by any differences that are observed between treatment conditions may be caused
refers to changes in the measuring instrument that occur during a research study in which participants are measured in a series of treatment conditions
Regression toward the mean
mathematical phenomenon in which extreme scores on one measurement tend to be less extreme on a second measurement
when the experience of having tested in one treatment condition (participating and being measured) has an influence on the participants' scores in a later treatment condition
occur when one treatment condition produces a change in the participants that affects their scores in subsequent treatment conditions
refers to changes in a participant's behavior or performance that are related to general experience in a research study but not related to a specific treatment or treatments
defined as changing the order i which treatment conditions are administered from one participant to another so that the treatment conditions are matched with respect to time.
- counterbalancing increases variance
- asymmetrical order effects
- ^ # of treatments creates order effects w/ counterbalancing
limitations of counterbalancing
present treatments in every possible sequence. A particular series of treatment conditions may create its own unique order effects.
used to construct a simple unbiased procedure for selecting sequences
- individual differences
- time-related factors
- fewer participants
three factors that differentiate within-subjects from between-subjects
each individual in one group is matched with a participant in each of the other groups. the individuals are equivalent with respect to a variable that the researcher considers to be relevant
duplicates all the advantages of a within and between w/o the disadvantages of either one
a researcher can easily maximize the differences between treatments by selecting two treatment conditions that are clearly different
a researcher can create a series of conditions and then observe how the participants' behavior changes as they move through the series of treatments. it also produces a more convincing demonstration of cause and effect relationship than is provided by a two-treatment.