Single- Subject Research Designs Chapter 14 1

Single- subject designs, or single- case designs, are research designs that use the results from a single participant or subject to establish the existence of cause- and- effect relationships. 2

Evaluating the Results from a Single. Subject Study • a single- subject design does not provide researchers with a set of scores from a group of subjects • Instead, the presentation and interpretation of results from a single- subject experiment are based on visual inspection of a simple graph of the data. 3

Example 4

Limitation • The results as presented do not represent a true experiment because there is no control over extraneous variables. 5

Phases and phase changes A phase is a series of observations of the same individual under the same conditions. When no treatment is being administered, the observations are called baseline observations. 6

3 types of baseline 1. Stable level 2. Stable trend 3. Unstable data 7

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Dealing With Unstable Data 1. The researcher can simply wait; occasionally, a participant reacts unpredictably to the novelty of being observed. 9

Dealing With Unstable Data 2. Consider the average of a set of two ( or more) observations. 10

Dealing With Unstable Data 3. look for patterns within the inconsistency. For example, a researcher examining disruptive classroom behavior may find that a student exhibits very high levels of disruption on some days and very low levels on other days she has a swimming lesson 11

Length of a Phase • To establish a pattern ( level or trend) within a phase and to determine the stability of the data within a phase, a phase must consist of a minimum of three observations. 12

When to Change Phases • When the data in a baseline phase show a trend indicating improvement in the client’s behavior, a researcher should not intervene by introducing a treatment phase. • Another possibility is that the baseline data indicate a seriously high level of dangerous or threatening behavior. In this case, a researcher probably should not wait for the full set of five or six observations necessary to establish a clear pattern. 13

When to stop treatment • If a treatment appears to produce an immediate and severe deterioration in behavior, we should stop the treatment 14

Visual Inspection Techniques • Unfortunately, there are no absolute, objective standards for determining how much of a change in pattern is sufficient to provide a convincing demonstration of a treatment effect. • The most convincing results occur when the change in pattern is immediate and large. 15

4 types of change • • Change in average level Immediate change in level Change in trend Latency of change. 16

1 - Change in average level 17

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2 - Immediate change in level • Comparing the last point in one phase with the first point in the following phase 19

2 - immediate change in level 20

3 - Change in trend 21

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4 - Latency in change 23

4 - Latency in change 24

The problem with single subject design 25

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THE ABAB REVERSAL DESIGN • the majority of single- subject research studies use ABAB design; • consists of four phases: a baseline phase ( A), followed by treatment ( B), then a return to baseline ( A), and finally a repetition of the treatment phase ( B). 27

Effective 28

Not Effective 29

Limitations of the ABAB Design • The clinician has implemented a treatment that has corrected a problem behavior, and when the treatment is removed, the correction continues. • A second problem with an ABAB design concerns the ethical question of withdrawing a successful treatment. 30

Variations on the ABAB Design 31

1 - B not working use C 32

2 - B not working add C B= Graduated exposure C= Reinforcement 33

3 - MULTIPLE- BASELINE DESIGNS 1 - Eliminates the need for a return to baseline and therefore, 2 - Is particularly well suited for evaluating treatments with long- lasting or permanent effects. 34

3 - MULTIPLE- BASELINE DESIGNS Examples A therapist uses the same method for 2 different behaviors (across behaviors) For one behavior that is exhibited in 2 different situations. (across situations) A teacher uses the same method on 2 different students (across subjects) 35

Person 1 Person 2 2 different students 36

Yelling Crying 2 different behaviors 37

School Home 2 different situations. 38

Weaknesses of the Multiple- Baseline Design? 39

Weaknesses of the Multiple- Baseline Design • The risk is that a treatment applied to one behavior may generalize and produce changes in the second behavior. (Treating stuttering may help treating aggressive behavior) • In a multiple- baseline study across behaviors, one behavior may show a large and immediate change, but the second behavior may show only a minor or gradual change when the treatment is introduced. • The same problem can occur with research involving different participants with similar behavior problems. 40

4 - Dismantling design A dismantling design, also called a componentanalysis design, consists of a series of phases in which each phase adds or subtracts one component of a complex treatment to determine how each component contributes to the overall treatment effectiveness. 41

Example 42

5 - The Changing- Criterion Design • The criterion level is changed from one phase to the next. 43

Smoking Treatment 44

6 -The Alternating- Treatments Design • In an alternating- treatments design, also called a discrete-trials design, two ( or more) treatment conditions are randomly alternated from one observation to the next. 45

Example 1 - Alternate weeks 46

Example 29 cases for each method 47

GENERAL STRENGTHS OF SINGLE- SUBJECT DESIGNS • Is conducted with only one participant or occasionally a very small group. • Tends to be much more flexible than a traditional group study. • Single- subject designs require continuous assessment. 48

General Weaknesses Of Single- Subject Designs • Participant’s behavior may be affected not only by the treatment conditions but also by the assessment procedures. • Another concern for single- subject designs is the absence of statistical controls. 49