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

It involves leaving the subjects in

the A condition.

Studies ended 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

Involves a 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 Which do 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?