1. Experimental Design
Dependent variable (DV): Variable observed to determine the effects of an experimental manipulation (behavior)
Independent variable (IV): Variable manipulated by the experimenter (environmental event or treatment)
Confounding variable: Source of influence other than the IV that may produce changes in the DV
Experimental design: Rules for applying an IV so as to examine its effects on a DV
Functional relation: A relationship in which changes in one variable (DV) are demonstrated to be the result (a function) of changes in another variable (IV)
Single subject design: An experimental design in which a functional relationship can be demonstrated with the behavior of only one subject
Baseline: Condition in effect prior to introduction of the IV
A-B notation system: “A” denotes baseline; subsequent letters (“B,” “C,” etc.) denote different IVs
Replication: Duplication of earlier conditions in an experiment

2. A-B Design
Definition: Single introduction of at least one IV on one baseline

3. A-B Design
Definition: Single introduction of at least one IV on at least one baseline
Advantage: Repeated measurement under BL (A) and Rx (B) conditions allows examination of changes in level, trend, and variability
Limitations:
No replication
Therefore, does not rule out the influence of confounding variables
Therefore, no demonstration of a functional relation

4. Reversal Design (ABA)

5. Reversal Design (ABAB)

6. Reversal Design
Definition: Introduction and subsequent removal of at least one IV on one BL
Variations: ABAB, ABA, BAB, ABAC, etc.
Advantage: Simple yet powerful demonstration of experimental control
Limitations:
Detrimental effects of reversal: Ethical considerations
Irreversibility: Failure to reproduce effect observed in a previous phase even though conditions are arranged identically
Sequence/Order effect: Influence of a previous manipulation on responding in a later condition (e.g., training  contingencies)

7. Irreversibility (suspected)

8. Multiple Baseline Design
Definition: Sequential introduction of an IV across more than one BL

9. Multiple Baseline Design
Definition: Sequential introduction of an IV across more than one BL
Variations: Across subjects, behaviors, settings
Advantage: Does not require reversal to show experimental control
Disadvantages:
Stability requirement more cumbersome than with a reversal design
Potential generalization across baselines (more likely with MBL across behaviors or settings)

10. Multiple Baseline Design (Apparent Generalization)

11. Multielement Design
Definition: Rapid alternation of BL and IV conditions (or 2 or more IVs) on a single BL

12. Multiple Baseline (generalization)
All of the designs we covered today aren’t mutually exclusive - components of different designs can be used in combinations. For example, if you encounter one of the limitations of a multiple BL - generalization across baselines / behaviors - then the original design isn’t providing experimental control. So, under those conditions, you might need to switch designs to demo experimental control.
What could you do in this case to show control?

13. Multiple Baseline ∆ into Reversal
Reversing back to BL at least allows you to show an effect on the first BL.

14. Reversal (irreversibility)

15. Reversal ∆ into Multiple BL across Subjects