A Time Series Design

me series designs employ many different types of intervention models to determine the effectiveness of treatments. The following sections are examples of the models most often used in time series designs.

Simple Phase Change

The simplest method for determining the impact of an intervention on a client is the simple phase change, or AB design, where A represents the baseline condition and B represents the intervention. Data collection during the baseline phase includes measuring the frequency, duration, and/or intensity of the client’s targeted behavior(s) before the intervention. After baseline data are collected, the intervention phase begins. The target behavior is again measured repeatedly and recorded. Data from both the baseline and the intervention phase are compared to determine the effectiveness of the intervention.

collecting baseline data

Baseline consists of repeated measurements of the target variable at equally spaced intervals over time. Considerations must be given to the type of measurement collected, how the measurements will be collected, the number of measurements obtained, and the time interval between measurements.

Measurements can reflect the magnitude, duration, frequency, or existence of a problem. Magnitude refers to the intensity or severity of beliefs, attitudes, moods, or emotions. Duration includes the length of time the problem occurs, while frequency is the number of times the problem occurs within the specified time period. Problem existence refers to the presence or absence of behavior, symptom, or problem (Tripodi, 1994).

According to Blythe and Tripodi (1989), measurements for baseline data can be obtained the following ways:

1. Observing and gathering measurements during problem assessment before any intervention.

2. Observing and gathering measurements on a specific problem while a separate intervention is being used to address a different problem than the one being baselined.

3. Reconstructing measurements based on archival data and available records, such as school grades, absences, and disciplinary referrals.

4. Gathering client’s recollections concerning targeted problem through a questionnaire.

(Sheperis 104)

Sheperis, Carl J., J. Young, M. Daniels. Current View: US Counseling Research: Quantitative, Qualitative, and Mixed Methods. Pearson Learning Solutions, 07/2009. VitalBook file.

The citation provided is a guideline. Please check each citation for accuracy before use.

As a counseling researcher, you will need to ensure that enough measurements are taken during baseline to establish stability. A minimum of three points is needed to determine trends if the measurements are similar (Barlow & Hersen, 1984; Jayaratne & Levy, 1979). However, you should gather as many measurements as needed to establish horizontal stability of the target behavior. That is, the measurements should form a line that is parallel to the x-axis on a graph (see Figure 8.6). However, if the targeted behavior is getting worse, you can end the baseline phase and begin the intervention without obtaining horizontal stability (Tripodi, 1994).

The decision for selecting the appropriate time intervals for measurement is based on your clinical judgment. The intervals should reflect a sufficient amount of time that would allow change to reasonably occur and should make clinical sense in relation to the client’s problem (Tripodi, 1994). For example, if measurements are taken every day, then data should be collected for about one to two weeks to determine trends.

Baseline data can provide information for assessing specific problems and evaluating interventions. The severity and persistence of a specific problem can be clearly examined, thus providing information for problem assessment. Baseline data can also serve as a frame of reference for comparing measurements before, during, and after an intervention to measure its effectiveness (Bloom & Fischer, 1982).

intervention phase

Following the baseline phase, you would introduce an intervention designed to meet the objective for treatment. You may strive to achieve change through an intervention or may actually desire no change if the intervention is used as a prevention method. You should describe the intervention in detail, including such information as names of person(s) providing intervention, location, frequency, and duration of intervention, and a description of the actual intervention strategy (Tripodi, 1983). By clearly describing the intervention, you can ensure consistent implementation of the intervention as planned, thus increasing reliability and validity (Blythe & Tripodi, 1989). You can design a checklist of intervention guidelines to ensure consistent implementation (Blythe & Tripodi, 1989) or develop a client questionnaire to determine if you followed the guidelines (Tripodi, 1994).

Procedures for taking measurements during the intervention phase must be consistent with those of the baseline phase. The problem variables as well as the time between measurements should be identical to that of the baseline phase. The number of measurements taken during the intervention phase will vary, depending on the following: when you expect to observe changes (or lack of changes in the case of prevention) in the problem variable; the extent to which the severity of the problem variable deteriorates during intervention; or early attainment of treatment objective. The number of measurements taken during the intervention phase should demonstrate persistent achievement of the treatment objective when compared with a horizontally stable baseline (Barlow & Hersen, 1984). The absolute minimum number of measurements, however, should be the same number taken during the baseline phase (Tripodi, 1994) (see Figure 8.7).

(Sheperis 104-105)

Sheperis, Carl J., J. Young, M. Daniels. Current View: US Counseling Research: Quantitative, Qualitative, and Mixed Methods. Pearson Learning Solutions, 07/2009. VitalBook file.

The citation provided is a guideline. Please check each citation for accuracy before use.

During the intervention phase, you should examine the measurements to determine whether or not change occurs. If the problem variable does not change, then you need to determine the reasons and whether or not to continue or modify the intervention. If the behavior changes after implementing the treatment, then there is strong evidence that the intervention changed the behavior. However, the simple phase change design does not necessarily demonstrate causation between the intervention and the target behavior, because other extraneous conditions may have influenced the behavior. You may either utilize an extension of the AB design, such as the ABA or ABAB, or replicate the intervention with another client to determine whether the behavior changed as a result of the intervention or due to extraneous conditions.

ABA Design

Counseling researchers may implement a third phase, which is referred to as follow-up, or ABA design. This phase involves the removal of the intervention to determine if the problem variable changes without intervention. Once the intervention phase has shown persistent achievement of the treatment objective, the intervention can be withdrawn and measurements for the follow-up phase can begin.

Measurements should include the same problem variable, the same counselor, and the same time interval between measurements as the baseline and intervention phases. The number of measurements taken, however, may vary. If the treatment objective indicates that the results of the intervention will last a certain amount of time, then measurements for follow-up are taken for that specified length of time. For example, if you expect treatment to last for a minimum of six weeks, then measurements are taken for a minimum of six weeks. If the treatment objective does not specify a length of time, then you should collect measurements until horizontal stability is established or for a minimum of eight measurements to detect any trend (Tripodi, 1994) (see Figure 8.8).

The ABA design can be used to determine if removal of the intervention leads to baseline behavior, which means the intervention was effective while being utilized. However, it is impossible to remove some interventions, especially if they include cognitive strategies that the client has learned and incorporated into his or her daily life. In this case, follow-up enables you to determine the lasting effects of a particular intervention and provide additional therapy as needed if the problem relapses. If the intervention is reintroduced, then the design becomes an ABAB design.

(Sheperis 105-106)

Sheperis, Carl J., J. Young, M. Daniels. Current View: US Counseling Research: Quantitative, Qualitative, and Mixed Methods. Pearson Learning Solutions, 07/2009. VitalBook file.

The citation provided is a guideline. Please check each citation for accuracy before use.

The ABAB design is stronger than the simple phase change and the ABA design because it reintroduces the intervention phase after collecting follow-up measurements. This design controls many threats to internal validity (maturation, history, expectancy, and multiple treatment interference) and more clearly demonstrates the connection between the intervention and the target behavior. Figure 8.9 provides an example of the ABAB design.

(Sheperis 106-107)

Sheperis, Carl J., J. Young, M. Daniels. Current View: US Counseling Research: Quantitative, Qualitative, and Mixed Methods. Pearson Learning Solutions, 07/2009. VitalBook file.

The citation provided is a guideline. Please check each citation for accuracy before use.

ABAC or Combined Simple Phase Change Design

Another extension of the simple phase change is the combined simple phase change design (ABAC). This design involves the comparison of two separate interventions. After implementing the first intervention strategy, you complete the follow-up phase and then introduces a new intervention (C). Measurements are taken during this phase and then compared with baseline, the first intervention, and follow-up phases. This allows you to determine if one intervention is more effective than another. Figure 8.10 provides an example of the ABAC design.

Conclusion

The simple phase change design and its extensions are extremely valuable for the practicing counselor. The simplicity of the design provides counselors with information for problem assessment as well as immediate feedback regarding the effectiveness of interventions for each client, thus making the counselor more effective.

(Sheperis 107-108)

Sheperis, Carl J., J. Young, M. Daniels. Current View: US Counseling Research: Quantitative, Qualitative, and Mixed Methods. Pearson Learning Solutions, 07/2009. VitalBook file.

The citation provided is a guideline. Please check each citation for accuracy before use.