Educational Research

1. Educational Research Chapter 10 Single-Subject Experimental Research Gay, Mills, and Airasian

2. Single-Subject Research • Topics discussed in this chapter • The unique characteristics of single-subject designs • External and internal validity • Designing single-subject research • Three types of single subject designs • Analyzing data • Replication

3. Single-Subject Research • Two unique characteristics • The sample size is one subject • Each subject serves as his or her own control • Notation • ‘A’ indicates a non-treatment phase usually referred to as a “baseline” • ‘B’ indicates a treatment phase • Examples • A-B-A indicates a non-treatment baseline phase followed by a treatment phase which is followed by a return to a non-treatment baseline phase • A-B-A-B indicates four phases of treatment (baseline, treatment, baseline, and treatment) Objectives 1.1, 1.2, 1.5

4. Single-Subject Research • Why use a single-subject design? • In some situations it is unethical to deny a control group treatment, so a single-subject design is the alternative • Denying Title I resources to children who qualify for them • In other situations there are low incidences of subjects available to participate • Children with specific special needs Objective 1.3

5. Single-Subject Research • External validity • The lack of external validity is the major concern with single-subject designs • Generalizability is addressed through multiple replications of the same treatment and design that produce similar results for a number of different participants Objective 1.4

6. Single-Subject Research • Internal validity • Internal validity is always a concern with single-subject research • Two major threats • Instrumentation • Specificity of variables • Controlling threats • Baselines are multiple measures of pretest performance • By repeating baseline measures over a period of time threats to internal validity can be controlled • History • Maturation Objectives 1.6 & 1.7

7. Single-Subject Research • Number of manipulated variables • Only a single variable should be manipulated in single-subject designs • Adding and withdrawing more than one variable becomes problematic in terms of analyzing the individual effect of either variable Objective 1.8

8. Single-Subject Designs • Three major categories • A-B-A withdraw • Alternating phases of baseline (A) and treatment (B) • Alternatives include the A-B-A-B design • Multiple baselines • The systematic addition of behaviors, subjects, or settings for intervention • Used when baselines cannot be recovered after treatment has been received Objective 1.9

9. Single-Subject Designs • Three major categories (cont.) • Alternating treatments • Rapid alternation of treatments to a single subject to assess the effectiveness of two or more treatments Objective 1.9

10. A-B Withdraw Design • The A-B design • O O O O O O O X O X O X O X O Baseline Treatment • Internal validity threats are of concern • Use of designs with additional baseline and/or treatment phases helps to control threats to internal validity Objective 1.10

11. A-B-A Withdraw Design • The A-B-A design • O O O O X O X O X O O O O O Baseline Treatment Baseline • If the outcome is better during treatment than either baseline, the treatment is likely effective • Internal validity threats can be controlled • The major concern • The experiment ends with the subject not receiving the treatment • If the treatment has been shown to be effective this is an ethical concern Objective 1.10

12. A-B-A-B Withdraw Design • The A-B-A-B design • O O O O X O X O X O O O O O X O X O X O Baseline Treatment Baseline Treatment • Internal validity threats can be controlled • The effects of the treatment can be demonstrated twice • If the results are the same, it is likely the influence of extraneous variables has been controlled • Ethical concerns related to the A-B-A design are eliminated • The right pattern of results provides convincing evidence of the effectiveness of the treatment Objective 1.10

13. Multiple Baseline Designs • Three basic multiple baseline designs • Across behaviors • Data are collected on several behaviors for a single subject • Treatment is applied to each behavior one at a time until all behaviors have been treated • Across subjects • Data are collected on several subjects for one behavior • Treatment is applied to each subject one at a time until all subjects have been treated Objective 2.1

14. Multiple Baseline Designs • Three basic multiple baseline designs (cont.) • Across settings • Data are collected on one behavior for one subject across several settings • Treatment is applied to each behavior one at a time in each setting until all settings have been treated Objective 2.1

15. Multiple Baseline Designs • Three basic multiple baseline designs (cont.) • An example across behaviors • Behavior 1 O O X O X O X O X O X O Behavior 2 O O O O X O X O X O X O Behavior 3 O O O O O O X O X O X O • Design concerns • If behaviors are treated the behaviors must be independent of one another • If subjects are treated the subjects must be similar • If settings are treated the settings must be as natural as possible Objective 2.1

16. Multiple Baseline Designs • Advantages • Can be used when baseline data are not recoverable after treatment • The effects of reinforcement are designed to be maintained after the reinforcement is removed • Can be combined with A-B-A designs to establish a very convincing case for cause and effect • An A-B-A design is applied across three behaviors Objective 2.2

17. Alternating Treatments Design • Involves the relatively rapid alternation of treatments for a single subject • Treatment does not occur at fixed time periods • Treatments are changed sporadically • Advantages • Useful in assessing the relative effectiveness of two or more treatments • No withdraw of treatment is necessary • No baseline is needed • The effects of treatment can be studied quickly and efficiently Objectives 3.1 & 3.2

18. Data Analysis and Interpretation • Two phases • An evaluation of the adequacy of the design • An assessment of the treatment effectiveness • Two techniques • Visual inspection of the data • Graphical presentation of the results Objective 4.1

19. Data Analysis and Interpretation • Significance • Clinical significance • Effects related to the behaviors being treated • Meaningful in a “real” sense • Parallels the importance of practical significance • Statistical significance • Statistical tests are available but often result in statistical significance that has little if any clinical significance • Use is currently debated in the field Objective 4.2

20. Replication • Replication is an important aspect of single-subject research • The more one’s results are replicated the more confidence one has in the procedures that produced the results • Three stages of replication • Direct replication • Same researcher, same subjects, specific setting • Simultaneous replication refers to the use of different subjects and increases the generalizability of the study Objectives 5.1 & 5.2

21. Replication • Three stages of replication (cont.) • Systematic replication • Follows direct replication efforts • Involves different researchers, behaviors, or settings • Over time techniques are identified that consistently produce effective results • Clinical replication • Follows systematic replication • Involves the development of treatment packages composed of two or more effective treatments Objective 5.2