The use of experimental and quasi-experimental single-case designs in psychology: Theoretical and methodological aspects

This article presents the basic principles of experimental and quasi-experimental single-case designs, as they can be used in psychology, in particular to evaluate experimentally the effectiveness of an intervention with a single individual. After reviewing the theoretical foundations of single-case research designs, the methodological requirements of quasi-experimental and experimental single-case designs are described. The primary features of each experimental design are detailed and illustrated by a study. Finally, different methods of evaluating data from single-case designs are presented and discussed.