Which description matches a single-subject design?

• A. Group generalization is the main goal.
• B. The focus is on the individual with repeated measurements to observe treatment effects.
• C. Random assignment to groups is required.
• D. Qualitative data are exclusively used.

Answer: (B)

Single-subject designs examine how one individual responds over time, using repeated measurements to show how an intervention affects that person’s behavior. In practice, you collect data during a baseline period and then during the treatment period for the same student, often plotting the data to visually assess whether the treatment produces a clear change that coincides with its introduction. This emphasis on the within-person trajectory and repeated measures is what distinguishes it from other designs.

The reason this description fits best is that it centers on studying the single learner with multiple data points to observe treatment effects, rather than comparing groups or drawing generalizations across a population. Group generalization and random assignment are hallmarks of group designs, not single-subject approaches. And while qualitative data can be part of case work, single-subject designs are not defined by using only qualitative data; they commonly rely on quantitative, time-series data to demonstrate a treatment effect within the individual.