1. Single-Subject Research
Chapter 11
Single-subject research usually involves collecting data on one subject at a time. Single-subject researchers generally use line graphs to illustrate the effect of their intervention.

2. Single Subject Research
“Single subject research (also known as single case experiments) is popular in the fields of special education and counseling. This research design is useful when the researcher is attempting to change the behavior of an individual or a small group of individuals and wishes to document that change. Unlike true experiments where the researcher randomly assigns participants to a control and treatment group, in single subject research the participant serves as both the control and treatment group. The researcher uses line graphs to show the effects of a particular intervention or treatment.  An important factor of single subject research is that only one variable is changed at a time. Single subject research designs are “weak when it comes to external validity….Studies involving single-subject designs that show a particular treatment to be effective in changing behavior must rely on replication–across individuals rather than groups–if such results are be found worthy of generalization” (Fraenkel & Wallen, 2006, p. 318).

3. Example of Single Subject Design in Real Life
So lets say you want to determine the best course of treatment for anxiety disorders. So you collect data on a group of subjects anxiety as baseline data - A (baseline period) - then you give subjects a variety of treatments: placebo, cognitive behavioral, and benzodiazepines - B (treatment period) - then you measure level of anxiety 6 months later - A (baseline period).

4. Suppose a researcher wished to investigate the effect of praise
Baseline Praise

5. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions

6. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

7. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred.
Baseline 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

8. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

9. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

10. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

11. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

12. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

13. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day for several days.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

14. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day for several days. In the example below, the target student was disruptive seven times on the first day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

15. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day for several days. In the example below, the target student was disruptive seven times on the first day, six times on the second day
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

16. Suppose a researcher wished to investigate the effect of praise on reducing disruptive behavior over many days. First she would need to establish a baseline of how frequently the disruptions occurred. She would measure how many disruptions occurred each day for several days. In the example below, the target student was disruptive seven times on the first day, six times on the second day, and seven times on the third day.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

17. Once a baseline of behavior has been established (when a consistent pattern emerges with at least three data points), the intervention begins.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

18. Once a baseline of behavior has been established (when a consistent pattern emerges with at least three data points), the intervention begins. The researcher continues to plot the frequency of behavior
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

19. Once a baseline of behavior has been established (when a consistent pattern emerges with at least three data points), the intervention begins. The researcher continues to plot the frequency of behavior while implementing the intervention of praise.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

20. In this example, we can see that the frequency of disruptions decreased once praise began.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

21. In this example, we can see that the frequency of disruptions decreased once praise began. The design in this example is known as an A-B design.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

22. In this example, we can see that the frequency of disruptions decreased once praise began. The design in this example is known as an A-B design. The baseline period is referred to as A
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

23. In this example, we can see that the frequency of disruptions decreased once praise began. The design in this example is known as an A-B design. The baseline period is referred to as A and the intervention period is identified as B.
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

24. In this example, we can see that the frequency of disruptions decreased once praise began. The design in this example is known as an A-B design. The baseline period is referred to as A and the intervention period is identified as B.
A B
Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

25. Another design is the A-B-A design
Another design is the A-B-A design. An A-B-A design (also known as a reversal design) involves discontinuing the intervention and returning to a baseline.
Baseline Praise Baseline 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

26. Another design is the A-B-A design
Another design is the A-B-A design. An A-B-A design (also known as a reversal design) involves discontinuing the intervention and returning to a baseline.
A B A
Baseline Praise Baseline 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

27. Sometimes an individual’s behavior is so severe that the researcher cannot wait to establish a baseline and must begin with an intervention. In this case, a B-A-B design is used. The intervention
Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

28. Sometimes an individual’s behavior is so severe that the researcher cannot wait to establish a baseline and must begin with an intervention. In this case, a B-A-B design is used. The intervention is followed by a baseline
Praise Baseline 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

29. Sometimes an individual’s behavior is so severe that the researcher cannot wait to establish a baseline and must begin with an intervention. In this case, a B-A-B design is used. The intervention is followed by a baseline followed by the intervention.
Praise Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

30. Sometimes an individual’s behavior is so severe that the researcher cannot wait to establish a baseline and must begin with an intervention. In this case, a B-A-B design is used. The intervention is followed by a baseline followed by the intervention.
B A B
Praise Baseline Praise 8 7 6 5 4 3 2 1
Frequency of disruptions
Day

31. Multiple- Baseline
Sometimes, a researcher may be interested in addressing several issues for one student or a single issue for several students. In this case, a multiple-baseline design is used.
“In a multiple baseline across subjects design, the researcher introduces the intervention to different persons at different times. The significance of this is that if a behavior changes only after the intervention is presented, and this behavior change is seen successively in each subject’s data, the effects can more likely be credited to the intervention itself as opposed to other variables. Multiple-baseline designs do not require the intervention to be withdrawn. Instead, each subject’s own data are compared between intervention and nonintervention behaviors, resulting in each subject acting as his or her own control (Kazdin, 1982).

32. Multiple- Baseline Example
Figure uses the multiple baseline design to determine if the timing of treatment is important.  Notice how the behavioral change took place for each subject immediately following the introduction of treatment.  This graph shows that the timing of treatment is not important but also shows that change is directly related to the treatment. 

33. Multiple- Baseline Example
Figure tells us a different story.  Had we only tested subject A, we might have assumed that the treatment effected the change.  Subjects B and C however, demonstrate that the treatment actually had no effect on the behavioral change.  In fact, the behavior changed at the same time for each subject regardless of when the treatment was applied.  Without the time-lagged approach of multiple baseline design, this phenomenon would have been missed.

34. Benefits and Limitations to Single-Case Designs