1 Single Subject Experimental Design The Evidence in EBP

2 Evidence-Based Practice (Sackett D et al. 2000) "Evidence-based medicine is the integration of best research evidence with clinical expertise and patient values."

3 Evidence Based Practice Model To provide high-quality services by the integration of: –clinical expertise, –best current evidence, and –client values

4 "evidence is never enough" the EBP framework acknowledges that the experiences, values, and preferences of ourselves and our patients

5 But still need to deal with it

6 Single Subject Experimental Design Research Efficacy of Intervention

7 Efficacy encompasses Effectiveness –Behavior change as a direct result of intervention Efficiency –Comparison of at least 2 effective treatment interventions, in terms of one more criteria: time, cost, error rate

8 Designs in Single-Subject Studies Phases –A phase – baseline –B phase – condition 2 Types of SSD –Descriptive A: Baseline only B: Intervention only A-B: Baseline-Intervention –Experimental (control) Examine cause-effect relationship

9 A-B Design Phase A - Baseline Phase B - Intervention

10 Problem with A-B Design Does not allow the evidence to rule out the threats to internal validity

11 Internal Validity Did in fact the experimental conditions make a difference in this specific instance? Threats to internal validity –Maturation/recovery –History (previous intervention) –Hawthorne Effect (testing effect)

12 ABA Design ABA design superior to AB design Demonstrates experimental control through introducing and withdrawing intervention

13 Potential Problems - ABA Design Design not common due to: –ethical issues –behavior not subject to changes on withdrawal

14 Reversal Design is applied when? Removal of experimental contingencies does not result in a return back to baseline Reversal is the application of experimental contingencies to an alternate behavior incompatible with the target behavior

15 ABAB Design – Example 1 Solves ethical issue Vaugh & Horner (1995) –Effects of concrete (symbol + spoken words) versus verbal modes for choice making –A: meal choices – verbal –B: choices – picture + verbal –Resulted in more acceptances with B phase

16 ABAB Design – Example 2 Rotholz et al (1989) –2 communication modes for requesting fast food –A- Choices w/ sign language –B – Graphic symbols –Results use of graphic symbols resulted in more successful requests than signing in community settings

17 Multiple Baseline Design Intervention is introduced sequentially across multiple baselines: –Behaviors –Settings –Subjects

18 Experimental Control in MBD comes with replication of intervention effects on another behavior (or subject), not a reversal or withdrawal of intervention

19 How to Study Efficiency –Comparison of at least 2 effective treatment interventions, in terms of one more criteria: time, cost, error rate

20 Alternating Treatment Design Comparison of 2 or more conditions

21 ATD – Appropriate for effectiveness? Make sure to control for order effects

22 Order Effects PRESENTATION ORDER OF ITEMS camel-bat-seal 1-3-2camel-seal-bat 2-3-1bat-seal-camel 2-1-3bat-camel-seal 3-1-2seal-camel-bat 3-2-1seal-bat-camel

23 External Validity Generalization -- The degree to which the results of a research study or experiment can be generalized to other groups, settings or situations. Problem for SSD Solution ?

24 Purposes of Single-Subject Designs* 1.Does this treatment work? 2.Which treatment is better? 3.What parts of a intervention package are doing the job? 4.Does changing the criterion for success lead to improved performance? Lubinsky (2004)