Single-subject experimental research involves studying the effect of an intervention on a single subject over time through repeated measurements. It is useful for clinical research like behavior modification and drug evaluation. The key aspects of single-subject design include establishing a stable baseline, introducing an intervention or manipulating variable, and taking repeated measurements of the target behavior under standardized conditions. Common basic designs are withdrawal, reversal, and multiple baseline designs which help evaluate the effectiveness of an intervention. Both overt and covert behaviors can be measured, and data is typically evaluated through visual inspection rather than statistics. Strengths include control of extraneous variables and ability to concentrate on one subject, while weaknesses include lack of generalizability and potential order effects.

1. N 1 RESEARCH
Dr. G. K. SELLA KUMAR, Ph. D.,
Professor & Director
AsiaN Institute of Psycho-Diagnostics and Behaviour
Research, Coimbatore – 641044

2. Single - Subject Experimental
Research
In the present type of experimental design in which
single subject (N=1) participate.
It is also referred as Single Case or N 1 (one) research
Usually one subject will participate and the effect of
interventions is vigorously studied over the same one
Individual over times.
Most of these studies includes more than one subject
–referred as Small N research.
To test a particular treatment will tend to have
an effect on one or more behaviors

3. Significance
Highly useful in clinical researches – especially
in behavior modification and drug evaluation
In fact it can be applied to variety of research
topics.
It is similar to three Quasi Experimental Design
1] Time –Series Design, 2] Equivalent Sample
Design and 3] Equivalent Pretest – Post Test
Design.
The only difference is that Quasi – Experimental
design group of subject used while Single –subject
design concerned with individual

4. Origin….
Origin of single –subject design
developed from case study design
According to Kazdin (1982) the
development of Single –subject research
design –I being currently practiced.
Largely an out growth of work of B. F.
Skinner- operant conditioning.
Popularly called – experimental analysis
of behavior contains many features and
characteristics single- subject design
Many of the animal Lab researches
included one or few subjects upon
where repeated measures and
observations were taken

5. General Procedures of Single –Subject
Experimental Design
Repeated Measurements
Baseline or operant level
Manipulating Variable
Length of phases

6. Repeated measurement
Important aspects of N 1 research is the repeated
measurement or observation of the same individual
over times
Purpose is to determine the effect of intervention
introduced in the experimental condition
More careful and systematic repeated observation
– the more valid and reliable data can be gathered.
To assure reliable and valid data, the measures to
be used must be clearly defined.
Researcher must be careful in selecting the
behavior to be observed and behavior should be
measured
Continued.
. .

7. Measurable behavior must be observed without any
hesitation, be ready to exhibit it with reasonable
degree of frequency.
Measurement procedure must include, tests, survey,
questionnaires, Opinionaire, attitude scales., etc.
Researcher must select such instrument that can be
used repeatedly without any contamination or test –
interaction effect
For enhancing the reliability and validity of S-S
research, the measurement must also be done under
completely standardized condition
Under standardized conditions- measurements are
to be repeated, maintain uniformity in the time of
day, circumstances, general surroundings such as
location, presence of others etc.
Same measurement procedure for each replication
of measurement

8. Baselines
– The baseline also called operant level.
– one of the important aspect of general procedure.
– Baseline is used to determine the status of the
subject’s behavior prior to the intervention by the
researcher.
– Baseline data are gathered by observing the aspects of
individuals behavior.
– It is to be studied several times prior to the
intervention by the researchers.
– It should be long enough in determining the trend of
data.
– Generally three types of trends are revealed by
baseline.
1 A stable rate.
2 An increasing rate
3 A decreasing rate.
For better evaluation of the effectiveness of the
intervention the baseline must demonstrate a stable
rate.

9. Baselines
Problem occur in the evaluation of effectiveness
of the intervention because the baseline, even
prior to intervention is showing trend.
A good baseline is formed only after minimum of
three separate observation.
However, 5 to 8 or even more observation will be
better.

10. Manipulating Variables
Single subject Research also requires manipulation
of variables .
Ideal condition is that in which one variable should
be manipulated at any given time.
If two variables manipulated at a same time – effect
of each can’t be separated – effect became un-
interpretable.
In such –variable can be manipulated one by not at
a same time.
For Ex:- Systematic desensitization and medication
on aggressive child.
B1- T1-B2, B2-T2-B3.

11. Length of phases
Sometimes first intervention has to be larger than the
initial baseline in order to demonstrate a obvious change in
behavior.
*Baseline- Intervention – Baseline.
What should be the length of the each of these phases?
Ordinarily there are three phases .
Relative length of the each of different phases should be
equal.
If it happens, subsequent, second baseline and second
intervention should be of the same length.
However, there is a potential danger in having larger
intervention phases – i. e Carry – Over = Effect
Short intervention periods tends to prevent carry over
effect (Bijou, et al 1969).

12. Basic Designs of S-S research
Three types of Basic designs are
commonly used
1. Withdrawal Designs
2. Reversal Designs
3. Multiple Baseline Research

13. Withdrawal Design
In which intervention or Experimental treatment
introduced following the baseline period is
withdrawn
There are three basic withdrawal designs
A-B-A Design
A-B-A-B design and
Alternating treatment design
Before the discussion of these three – it will
be proper to start with A-B design – simplest
research strategy

14. A-B Design
Simplest Design for N = 1 Research
A Baseline (A) for a behavior is established and
subsequently predicted the behavior would continue to
exist if no treatment is administered.
If the following interaction (B) the behavior would
depart from the prediction
The researcher may attribute such change has
occurred due to the effect of treatment.
Continued. .
.

15. The researcher concludes that his intervention is effective in
producing a change – but it is weak because of the following
reason.
The researcher does not know what the
response rate might have been have no
treatment been administered
Researcher does not know certainly whether
any response change was produced because of
the specific intervention.
It might have changed just because the
researcher did something different.
This is called placebo effect – one of the
limitation of this design.

16. A-B-A Design
A-B-A Design important and popular design used in S-S research.
This design has baseline (A) – intervention (B) and baseline (A)
sequence.
The design has three phases, each of which represents a series of
measurement.
Behavior is studied to examine whether it changes from (A)
baseline or control condition to (B) the treatment condition, which
or not it comes back to to baseline (A) if the treatment or
intervention is withdrawn
The behavior actually increases during treatment
Decreased following withdrawal of intervention and then comes to
the level of the Baseline (A).
A sufficient reason is established - for the response changes is a
function of manipulation of independent variable or intervention
period.
A-B-A design is more powerful and convincing
yields more reliable and valid data.
Intervention withdrawal produce a return of response measure to
baseline- is confirmed

17. A-B-A-B design
Intervention is reintroduced after withdrawal
phase- this results A-B-A-B design
Operant level or baseline (A) And intervention (B)
each is repeated twice.
According to this design the behavior may change
from
1) (A) to (B) i.e Baseline to intervention
(Increases)
2) (B) to (A) i.e withdrawal of (B) to (A)
( Decreases)
3) (A) to (B) i.e behavior may increase with the
introduction of intervention (B) and the
behavior measure is strengthened
A-B-A-B design provides a better opportunity for
careful examination of intervention effect than the
simple A-B-A design

18. Alternating Treatment design
Sub class of A-B-A-B design
A and B are the two different treatments
Treatments A is withdrawn and replaced not by
baseline but by another treatment B
Purpose is to evaluate the relative effectiveness of
two or more than two treatments
Researches may come to the conclusion that
method A is better than method B or vice –versa.
The advantage is the treatment is used without
withdrawal and return to baseline.

19. 2 Reversal Design
In this design usually two alternative incompatible
behavior on chosen and researcher establishes the
baseline for each behavior
one behavior is subjected to one type of
experimental treatment and the other alternative
and incompatible behavior is subjected to another
type of experimental treatment
Baseline for both the behavior would be established
separately.

20. Multiple Baseline Design
I ) Multiple baseline design across behavior
II ) Multiple baseline design across subject
III ) Multiple baseline design across conditions or
environment.

21. Multiple Baseline Design Across
Behavior
The effect of independent variable s across several
different behaviors emitted by the same subject is
evaluated
He establishes baseline for each behavior
Subsequently a treatment is introduced for one target
behavior
If behavior changes – due to treatment abd other
behavior ( control) remains stable at the baseline –
concludes that the treatment is effective
After sometimes the treatment is applied to the second
target behavior and so on.

22. II ) Multiple baseline design across subject
A behavior is applied in sequence to the same class
of behavior in different participants in the same
environment
Another application is the same treatment is a
applied in different behavior emitted by a single
treatment
When treatment is applied to the same behavior of
different persons in the same in environment
sometimes – gap is followed
One participant after one Hr of establishing baseline
to a second after two Hrs of establishing baseline –
time lagged control design

23. III ) Multiple Baseline Design Across
Conditions or Environment.
Treatment is applied to the same behavior when
participants are in different environmental conditions
Researcher may have four different patients in 4
different rooms
Different baseline periods may be established each of
these four patients.
If there is response increment in all patients following
the interventions ,the treatment is likely to be effective
Contrasts to the withdrawal design – no need to
withdrawal the treatment once it has been applied

24. Data collection strategies
Two types of behaviors are commonly studied
1) Overt Behavior
2) Covert Behavior
Major data collection procedure is the observation of
an Overt behavior. In S-S research a number of ways
to measure Overt behavior. They are..
1) Frequency
2) Duration
3) Method of interval recording
4) Real Time observation method
Continued….

25. If the behaviors are not Overt the above measures are
not employed. In such situation other method of data
Collection are used .They are ..
1) Psycho-Physiological measures
2) Self- report measures
3) Response-Specific measures

26. Evaluating Data
Commonly Evaluated through visual inspection
Statistical Analysis is rarely used to analysis the effect
of intervention
Changes in the magnitude and rate of behavior being
studied
Average rate of performance and the level at the
change point should be examined – No of occurrence/
No of session
Change in the level - Shift in performance-fo end of
one phase to start of next phase
Show systematic changes –i.e +ve or –ve over time.
Tendency of change –How quickly change in response
occurs after beginning the treatment or withdrawal of
treatment – ensures the effectiveness of treatment.

27. Strength and Weakness
Carry out a scientific
investigation with only
one subject
Saves time in dealing
with many subject
Able to have full
concentration on only
one subject
Experimental situation
effectively through out
the research
Advantage for those who
dislike statistical
computations
Inappropriateness-
survey and Ex-post
facto
Practical limitation
– Time consuming
– Carry out only one
session
– Ss must be willing to
participate
– Cooperation by
giving sufficient time
– Difficult to measure
repeatedly
Order of effect -
results in
confounding and
limiting the quality
of generalization

28. Strength and Weakness
Irreversible effects
Descriptive and
Evaluative research
can be easily carried
out
Eliminate and hold
Constant extraneous
variable
Intra- subject
comparison is better
than inter subject
comparison - in
control of extraneous
variable
Irreversible effects
Lack of
effectiveness of
treatment
Researcher’s bias
Dependent
behaviors
Lack of external
validity
Magnitude of
effects

29. S-S Research and Large N Research
Control techniques
Manipulating the dependent variable
Monitoring the experimental data
Data analysis
External Validity of the results
Thus, S-S research differs considerably from large N
research in various important aspects such as employing
control techniques ,data analysis , generality of data etc.,

30. References
Singh, A. K. (1997). Tests, Measurements and
Research methods in behavioral sciences 2nd
Editon Bharathi Bhawan P.P 335-345.
Broota, K. D. (1985). Experimental Research in
Behavioral Research. Wishley Publishing
Company. New Delhi.p.9