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QUANTITATIVE RESEARCH
METHODOLOGIES

SINGLE-SUBJECT
RESEARCH

ESSENTIAL
CHARACTERISTICS
Data are collected and
analyzed for only one subject
at one time.
Most commonly used to study
the changes in behavior

THE GRAPHING OF
SINGLE-SUBJECT DESIGNS
Researchers primarily use line
graphs to;
Present their data
Illustrate the effects of a particular
intervention or treatment.

THE A-B DESIGN
 Collecting data on the same subject,
operating as his or her own control under
two conditions or phases.
 First condition (A); pretreatment condition

 Second condition (B); treatment or
intervention condition, introduced and
maintained for a period of time.
 figure 14.2 A-B Design.jpg

DISADVANTAGE OF A-B DESIGN

Researcher does not know
whether any behavior
change occurred because
of the treatment.

THE A-B-A DESIGN
 Sometimes called reversal design
 Researchers simply add another
baseline period
 To get stronger evidence for the
effectiveness of the intervention
 Reduce threats to internal validity

 figure 14.3 A-B-A Design.jpg

DISADVANTAGE OF A-B-A DESIGN

Itinvolves leaving the subjects in
the A condition.

Studiesended without some
degree of final improvement.

THE A-B-A-B DESIGN

 Two baseline periods are combined with two
treatment periods.
 Permits the effectiveness of the treatment.

 Avoids leaving subject without an intervention.

 Demonstrate that dependent variable changes as
independent variable is applied.

 figure 14.4 A-B-A-B Design.jpg

DISADVANTAGES OF A-B-A-B DESIGN

The possibility of data-collector
bias

An instrumentation effect; need for
an extensive number of data
collections period

THE B-A-B DESIGN

 Involvesa treatment followed by a
baseline by a return to the treatment.

 Appropriate when there is a lack of
behavior.

 figure 14.5 B-A-B Design.jpg

THE A-B-C-B DESIGN

 Further modification of the A-B-A design.

 The intervention is changed to control for any
extra attention the subject may have received.

 Contingent(or selective) praise is critical for
improved responsiveness.

 figure 14.6 A-B-C-B Design.jpg

MULTIPLE-BASELINE DESIGNS

 Researcher do more than collect data on one
behavior.
 They collect on several behaviors for one
subject.
 Researchers systematically apply the
treatment at different time for each behavior.
 figure 14.8 Multiple-Baseline Design.jpg

 Treatment is applied to change behaviors
accordingly.

THREATS TO INTERNAL VALIDITY

1. Condition length
2. Number of variables changed when moving
from one condition to another.
3. Degree and speed of change.
4. Return to baseline level
5. Independence of behavior
6. Number of baseline

THINGS TO PONDER
 Whichdo you think is easier to
conduct: single subject or group
comparison research? Why?

 What sorts of behaviors might require
only a few data points to establish a
baseline?

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Presentation edu 702

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