Single Subject Experimental Study

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