In a single-system design, which phase typically occurs first?

In a single-system design, the first phase is indeed the baseline phase, often referred to as the A phase. This phase is critical because it establishes a reference point against which the effects of any subsequent intervention can be measured. By collecting data during the baseline phase, a researcher can assess the initial conditions and behaviors before any intervention is applied.

This foundational phase allows social workers to observe any natural fluctuations in the data over time, providing insight into the client's situation or the issue at hand. Once the baseline data is collected, any changes that occur after the implementation of the intervention can then be compared to this original data, providing a clearer picture of the intervention's effectiveness.

Understanding the importance of the A phase in the research design helps social workers systematically evaluate interventions and make evidence-based decisions in their practice.