In the social sciences, the concept of methods “triangulation” dates to the work of
Campbell and Fiske (1959) who propose the use of more than one research method as part
of a validation strategy to ensure the explained variance is the result of the underlying
phenomenon and not an artefact of the research method adopted. Subsequent
researchers elaborate on the nature of methods triangulation, distinguishing
within-methods triangulation (the use of multiple quantitative or multiple qualitative
elements) from between-methods (the use of both quantitative and qualitative
elements)[1] and delineating method triangulation from data, investigator and theory
triangulation[2] (Webb et al., 1966). Studies have been considered mixed on the basis of:
addressing two types of research questions; the manner in which research questions are
developed; adopting two types of sampling procedures, data-collection techniques, types
of data or data analysis; and presenting two types of conclusions (Tashakkori and
Creswell, 2007b)