Triangulation as a basis for diagnostic judgments

Abstract The methodological concept of triangulation is discussed with special reference to the principles and procedures of triangulation as a general basis for diagnostic judgments. It is emphasized that triangulation always requires theoretical considerations. An action‐theory approach is introduced that provides the potential to establish such a concept. The differentiation between triangulation of data, criteria, and participants is explained and examples for the process of triangulation are provided. Finally, design triangulation is proposed to be used in extensive research processes in which large‐N studies, small‐N studies, and single case analysis complement each other.