Single-Subject Designs Popular within several areas of psychology. Long tradition in experimental psychology prior to development of modern statistics. Instead of many participants - use only one. No statistics - statistics look at variance among scores. Sometimes more than one subject is used and these are considered to be replications.
Researcher looks at graphs instead of using statistics.
Data are visually examined. Philosophy behind small n design is different than with multiple n design. B.F. Skinner Skinner criticized the use of multiple-subjects designs. Skinner believed that these obscure true changes in behavior. The statistical average is an abstraction that doesn't actually exist.