Term | Definition |
Experimental Design | Repeated, systematic presentation and
removal of an independent variable (or IV)
While measuring changes in the dependent
variable (or DV) and holding other factors
constant |
The primary goals of systematic experimental manipulation | To demonstrate a functional relation between the IV and DV and to evaluate the interventions once they are decided upon |
Functional relation | Changes in an antecedent or consequent stimulus class consistently alter a dimension of a response class |
Internal validity | The extent to which an analysis assures that
measured changes in behavior are due to the manipulation and not due to uncontrolled
extraneous variables. |
External validity | The extent to which a study’s results are generalizable to other subjects, settings, or behaviors. |
Threats to internal validity | History
Maturation
Testing
Instrumentation
Diffusion of treatment
Regression towards the mean
Selection bias
Attrition |
History | Introduction of the IV may coincide with other events in the person's life |
Maturation | Natural developmental events of learning experiences may coincide with the introduction of the IV to produce the change |
Testing | Changes in the DV may have come about as a function of repeated exposure to the experimental arrangements (e.g. practice effects) |
Instrumentation | Changes may reflect modifications in the measurement systems rather than effects of the IV |
Diffusion of Treatment | Inadvertent, uncontrolled "seepage" of the treatment to control conditions or control subjects |
Regression towards the mean | Changes occurred because baseline measurements were NOT representative of the natural stare of events (less relevant in SCD because of repeated measure) |
Selection bias | The assignment of subject to groups may have biased the outcome even in the absence of any intervention (less relevant in SCD because each participant serves as own control) |
Attrition | The loss of subjects over time, especially if systematic, may influence the effects (less relevant in SCD because each participant serves as own control) |
Minimizing Validity Threats | Measurement
Stability
Immediacy
Replication |
Single-Case Designs | The repeated and systematic presentation and removal of a treatment and measurement of behavior while holding other factors constant |
Baseline | Assessment of the dependent variable prior to the introduction or change of the independent variable |
Phase Change | Movement in the analysis from one level or kind of independent variable to the next level or kind of independent variable |
A-B Design | Baseline phase followed by a treatment
phase effect is demonstrated when behavior changes from one phase to the next |
Withdrawal Design | Baseline is followed by a treatment
condition. |
Reversal Design | An intervention is applied to the target
behavior after a baseline phase |
Multiple Baseline Design | Two or more independent baselines are
established. The IV is then separately introduced in a staggered fashion to each BL. When bx is stable for the first baseline, the IV is introduced on the second baseline, and so on |
Multiple probe technique | First baseline is continuous, but subsequent
baseline data collection is conducted on an
intermittent basis relative to the first baseline |