This paper, written by T. R. Kratochwill , J. Hitchcock, R. H. Horner , J. R. Levin, S. L. Odom , D. M. Rindskopf and W. R. Shadish for What Works Clearinghouse, looks at single-case designs (SCD) with a specific emphasis on developing a set of standards for their use. The paper also provides an overview of SCDs, specifies the types of questions that SCDs are designed to answer, and discusses the internal validity of SCDs.
"SCDs are adaptations of interrupted time-series designs and can provide a rigorous experimental evaluation of intervention effects (Horner & Spaulding, in press; Kazdin, 1982, in press; Kratochwill, 1978; Kratochwill & Levin, 1992; Shadish, Cook, & Campbell, 2002). Although the basic SCD has many variations, these designs often involve repeated, systematic measurement of a dependent variable before, during, and after the active manipulation of an independent variable (e.g., applying an intervention). SCDs can provide a strong basis for establishing causal inference, and these designs are widely used in applied and clinical disciplines in psychology and education, such as school psychology and the field of special education."
Kratochwill, T. R., Hitchcock, J., Horner, R. H., Levin, J. R., Odom, S. L., Rindskopf, D. M. & Shadish, W. R. (2010). Single-case designs technical documentation. Retrieved from What Works Clearinghouse website: http://ies.ed.gov/ncee/wwc/pdf/wwc_scd.pdf.