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Use Figure 9.1 to answer questions 1 and 2 of the Pre-Test.

  1. What is the meaning of the letters A and B in the graph in Figure 9.1?

  2. What conclusions could you draw from the graph of data?

  3. What characteristic(s) of single-subject studies are different from a randomized clinical trial?

  4. What are the primary differences between qualitative and quantitative research designs?

  5. What types of clinical questions are best addressed with a qualitative research study?


Example of an SSR design with one baseline phase (A), one treatment phase (B), and one withdraw of treatment phase.


We include single-subject and qualitative research in this chapter. These two types of research are not common in the physical therapy literature, but both types are useful for clinical decisions (Fig. 9.2). Many of the appraisal concepts described in depth in previous chapters can be applied to single-subject research;1 therefore, they are mentioned but not repeated in depth in this chapter. The different concepts used in the appraisal of qualitative research are described in more depth.


Both SSR and qualitative research are useful for clinical decisions.

Single-Subject Research

Understanding single-case experimental designs, analyses, and applications improves your ability to evaluate the evidence based literature and eventually to answer your clinical questions. Rigorous research with single participants can be applied to your patients, sometimes more directly than the results of group randomized clinical trials (RCTs). In a typical single-subject design (SSD) one participant is followed intensely. During a baseline period, before intervention begins, the variables of interest are repeatedly measured. This may occur over successive days or weeks. The baseline period establishes what is typical for each of the variables for the participant. For example, during a baseline period, the gait characteristics of a participant walking on a treadmill might be measured every day for a week. The intervention period begins after baseline and then data are collected periodically on the single subject during the intervention. There might then be a period after intervention, during which the participant is measured, but no treatment is given. The change in the variables during the treatment period is then compared to the variables during baseline and post-treatment periods. An SSD typically creates abundant data, but on only one participant.

In contrast to an SSD, case studies are typically written retrospectively and detail the characteristics of one case and the course of intervention for that case. A case study is not a controlled single-case experimental design and the two terms should not be interchanged. A case study is a systematically reported single-patient example that does not include a controlled manipulation of intervention or the other ...

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