Testing a process theory with an individual case? A hermeneutic method based on quantitative data

Abstract

Single case research is an appropriate way to investigate how psychotherapy works. Many corresponding theories already exist. However, this process theories must be tested. For various reasons, a purely quantitative design would not be sufficient in individual cases. Qualitative methods are generally more appropriate. Testing a theory, however, is a deductive-nomological research objective, which is usually regarded as incompatible with qualitative methods. In order to justify the testing of a theory as a deductive-nomological research objective with qualitative methods in a single case, the present study proposes a methodology, which turns the usual relation around: A deductive question is answered by an abduction. This act of interpretation for the theory test is implemented systematically with a new hermeneutic method. This qualitative method uses a broad quantitative data base as inductive part.