Educational Research

Chapter 10Single-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 needsObjective 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 receivedObjective 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 OBaseline 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 OBaseline 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 OBaseline 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 OBehavior 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

efficientlyObjectives 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 treatmentsObjective 5.2