Single system design, sometimes referred to as Single subject design is a longitudinal study of one person, family, or group. It is a study of repeated measures with data collected over time. It is often utilized as for analyzing change between measurements. They have the following components:
- One participant
- The baseline is the measurement at pretest
- Intervention with measurement repeated
- Introduce treatment + measure / assess for improvement change in behavior
For example, if someone was to study the smoking habits of one person. In the graph below, the baseline is the amount of cigarette that the participate smoked a day before the intervention is implemented. After a period of time an intervention is implemented (i.e. utilizing the patch, nicorette gum... etc). Part B is known as the treatment phase. It shows the amount of cigarette smoked by the participate after the intervention.
For further information regarding single system design studies you can view the study I completed on myself, Turn Your Life Upside Down: An Individual Design Study.