Single Subject Research Design

Definition 

A single subject research design is a sort of research methodology that involves evaluating a single phenomena (typically a behavior) over time. It is commonly used to evaluate interventions. A researcher might, for example, create a baseline of studying behavior for a disruptive student (A), then introduce a treatment including positive instructor attention (B), and finally switch to a treatment containing moderate punishment for not studying (C).

Breaf Story

In communication sciences and disorders (CSD) research, single-subject experimental designs (SSEDs) have a long history. SSED techniques were studied in a number of key research dating back to the 1960s and 1970s (e.g., Hanson, 1978; Haroldson, Martin, & Starr, 1968; Martin & Siegel, 1966; Reed & Godden, 1977). In the 1980s and 1990s, several reviews, tutorials, and textbooks detailing and encouraging the use of SSEDs in CSD were published (e.g., Connell, & Thompson, 1986; Fukkink, 1996; Kearns, 1986; McReynolds & Kearns, 1983; McReynolds & Thompson, 1986; Robey, Schultz, Crawford, & Sinner, 1999). SSEDs are commonly disregarded in modern discussions of evidence-based practice, despite their long history of usage in CSD. This article gives a detailed summary of SSEDs that are particular to evidence-based practice challenges in CSD, which may be utilized to inform disciplinary research and clinical practice.

The tools supplied by SSEDs are relevant for both researchers and practitioners in the present context of evidence-based practice. Evidence-based practice is defined by the American Speech-Language-Hearing Association (ASHA; 2005) as "an strategy in which current, high-quality research evidence is incorporated with practitioner experience and client preferences and values into the process of making clinical decisions." SSEDs are appropriate for therapeutic applications since they focus on the individual customer. The potential power of SSEDs' internal validity allows researchers, therapists, and educators to raise issues that standard group designs would not be able to answer. Clinicians and researchers should be conversant with the application, interpretation, and interaction between SSEDs and evidence-based practice because of these advantages.

Single-subject curriculum or single-case research design (SCED) is a study design most commonly employed in practical fields of psychology, education, and human behavior in which the subject acts as his or her own control rather than employing another individual or group in the design of experiments. Single-subject designs are preferred by researchers because they are more sensitive to individual organism differences than group designs, which are more sensitive to group averages. 1) Prediction, 2) Verification, and 3) Replication are the three pillars of single subject designs. The baseline data confirms the consequent and forecasts behavior. Verification is the process of proving that baseline responses would have continued if no intervention had been used. When a previously observed behavior changes, replication takes place. [1] Although a single-subject design can accommodate a high number of subjects, it is still a single-subject design because the subject serves as their own control. [2] In practical research, these designs are generally used to assess the impact of a variety of interventions.

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Types of Single Subject Design

Single-subject designs come in a variety of shapes and sizes.

Reversal design

Reversal design entails measuring behavior in a certain context three times in a row (ABA): baseline, intervention, and return to baseline. Extending the ABA design with repeated reversals (ABAB) and including additional treatments are examples of variations (ABCABC). The use of AB designs, or reversal designs that do not return to baseline, is not considered experimental. Because there is no replication in AB designs, functional control cannot be determined.

Alternating Treatments Design

The effects of two or more independent variables on the dependent variable are compared using the alternate treatments design (ATD). A no-treatment control condition and a final best-treatment verification phase are among the variations.

Multiple baseline design

Multiple baseline design entails taking baseline measurements on two or more behaviors, contexts, or persons at the same time. The IV is applied to one behavior, setting, or person while the baseline is maintained for the rest. The multiple probe design and the delayed multiple baseline design are two examples of variations.

Changing Criterion Design.

The effects of an IV on the steady improvement of a behavior already in the participant's repertoire are evaluated using changing criterion designs.

Limitation

Most information about who will get the intervention and when it will be introduced are decided prior to the start of the study in traditional research designs. In single-subject designs, however, these judgments are frequently made as the data is gathered. Furthermore, there are no universally accepted standards for changing phases, which could lead to disagreements about how a single-subject design research experiment should be done. The following are the key criticisms of single-subject designs:

• Carry-over effects are when the results of one phase are carried over to the next.
• The order (sequence) in which the intervention or treatment is delivered has an impact on the outcome.
• Irreversibility: A change in the independent variable affects the dependent variable in some withdrawal designs. Simply eliminating the independent variable will not undo this.
• Ethical Problem: Withdrawal of treatment under the withdrawal design can occasionally cause ethical and feasibility issues.

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