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Research Summary
Decision-Making
Polaha, J. A., & Allen, K. D.
(1999). A Tutorial for Understanding and Evaluating
Single Subject Methodology. (Proven Practice: Prevention
and Remediation Solutions for Schools, 1(2),
73-77.)
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Short Summary of Article:
Single-subject research is most popular in schools
because it is relatively inexpensive and easy to
manage, data can be evaluated without statistics,
and results highlight individual differences in
children. Single-subject research should include
repeated measurements of behavior over time, a
well-established baseline, stability in performance
before conditions are changed, the introduction of
only one change at a time, and the replication of
treatment effects within the same individual or
across individuals.
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Group research includes a control group
with individuals who do not receive the targeted
intervention and an experimental group with
individuals who do receive the targeted intervention.
Descriptive statistics describe average performance of each
group and inferential statistics are used to test the
statistical significance of differences between groups.
Single-subject research does not rely on
statistics to interpret meaningfulness. Single-subject
research is popular in schools because it is relatively
inexpensive and easy to manage, because data can be
evaluated without complicated statistics, and because
results highlight individual differences in children.
Features of single-subject research include:
1. repeated measurements of a behavior over time
2. a well-established baseline
3. stability before conditions are changed
4. the introduction of only one change at a time,
and
5. the replication of treatment effects within the
same individual or across individuals.
Some different single-subject research designs
include:
1. A-B Case Study design- A- baseline,
B-intervention
2. A-B-A and A-B-A-B reversal designs- most
conservative of designs, multiple baseline design- series
of A-B designs that are replicated with:
a. the same individual across a number of
behaviors
b. the same individual across a number of
settings
c. the same behavior across different
individuals
3. Changing criteria design- replicate A-B treatment
effects by repeatedly using each phase of the design as a
baseline for the following phase, intervention remains
the same but criterion for success changes until desired
outcome is achieved.
When reading single-subject studies ask
yourself:
1. How many of the five features were used?
2. Is there a clear separation in the data under one
condition compared with other conditions?
3. Did the investigators use standard and comparable
displays across graphs?
4. What was the time frame?
5. Were any follow-up data collected to evaluate
long-term impact?
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