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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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