Single-subject research designs focus on intensively studying individual participants. They involve establishing a baseline measurement of a participant's behavior, implementing an intervention, and measuring the impact on the behavior. Common single-subject designs include A-B, which measures behavior during a baseline and intervention phase, and A-B-A-B, which measures behavior across multiple baseline and intervention phases. These designs allow researchers to determine causal relationships between interventions and behavior changes. Replication of studies' results is important to validate the effectiveness of interventions.

1. Educational Research
Chapter 10
Single-Subject Experimental Research

2. What is single subject
research?
 Single-subject research is a quantitative research
that:
 involves studying in detail the behaviour of each of a
single or small number of participants
 focuses on understanding objective behaviour
through experimental manipulation and control,
collecting highly structured data, and analyzing those
data quantitatively.

3. Objectives of single subject
 To focus intensively on the behaviour of individual
participants.
1. - Group research can hide individual differences and
generate results that do not represent the behaviour
of any individual. Single-subject research, however,
would likely reveal these individual differences.
2. - To focus intensively on individuals is that
sometimes it is the behaviour of a particular
individual that is primarily of interest.

4. Objective of single subject
 To discover causal relationships through the
manipulation of an independent variable, the careful
measurement of a dependent variable, and the
control of extraneous variables.

5. Why single subject instead of
group approach?
 In some situations it is inappropriate/unethical to use
a control group treatment, so a single-subject design
is the alternative
 In other situations there are low incidences of
subjects available to participate. Eg: Children with
specific special needs

6. Single subject research
approach
 Single subject design involves single individuals or
small sample (n<10) and focus intensively on the
behaviour of individual participants and investigate
the effectiveness of an intervention.
 The researcher establishes the baseline behaviour or
actions by observation or multiple tests each day for
a set amount of time.
 After the baseline is set, an intervention would be
introduced to change or better the behaviour.
 This would be an A-B design where there is a simple
baseline phase and an intervention phase.

7. Single subject experimental
 Depending on the circumstances and needs, A-B-A design can
occur where the baseline is monitored, the intervention is
introduced and then the intervention is taken away to see
whether it helped long term or whether it is a shot term effect
only.
 The A-B-A-B design monitors the progress and investigates
what happens if the intervention is taken away, however it is
later put back in again to better the behaviour.

8. Single-Subject Research
 Two unique characteristics
 The sample size is one subject (individual/group/class) or
small group of sample (<10)
 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

9. 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

10. 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 in terms of
 History
 Maturation
Objectives 1.6 & 1.7

11. 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

12. Single-Subject Designs
 Three major categories
1. A-B (Basic design)
2. A-B-A, A-B-A-B withdraw
 Alternating phases of baseline (A) and treatment (B)
3. Multiple baselines
 The systematic addition of behaviors, subjects, or
settings for intervention
 Used when baselines cannot be recovered after
treatment has been received
4. Multiple treatment
Rapid alternation of treatments to a single subject to
assess the effectiveness of two or more treatments
Objective 1.9

13. 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

15. 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

18. 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

21. 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
 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

22. 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

23. 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

29. 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

33. 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

34. 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

35. 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

36. 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

37. Example -Single subject design
 A-B-A-B – this would be useful in a class where a child is not
learning times tables.
 A: Hypothetically their baseline progress would be tracked over a
weeks’ time where the child answers mathematical test.
 B: Then an intervention would be introduced where the child
practices for 10 minutes before sitting the daily test.
 A: To monitor how they do without the intervention, the new
baseline would be monitored again, and
 B: Then a more intense intervention could be introduced where the
child practices twice a day for 20 minutes.

38. Single subject experiment vs
Case study
 Single subject designs focus purely on single
individuals and investigate the effectiveness of an
intervention.
 Case studies are non-experimental observations that
are going to happen, or have happened due to
natural or economic or personal causes.

39. Single subject experiment vs
Case study
 There are two different types of case studies, the
retrospective and the prospective case studies.
 In the retrospective case studies psychologists
observe and/or measure the behaviour and activity of
the cases with a control group to measure the effects
the occurrence had on the subjects.
 In the prospective case study psychologists measure
the individual before they undergo the occurrence
and after they experienced the occurrence.

40. The End