Why should a researcher use mixed methods and/or methodologies?
Mixed methodology finds its roots in the work of Campbell and Fiske (1959) from which Denzin (1970) later developed the concept of triangulation. In its initial meaning, triangulation stood for convergence or confirmation of findings across different methods. Following this pioneering work, Greene et al. (1989, 1997a, 1997b) advanced five rationales or purposes for why researchers should use mixed methodologies.
Triangulation tests the consistency of findings obtained through different instruments. Triangulation will increase chances to control, or at least assess, some of the threats or multiple causes influencing our results.
Complementarity clarifies and illustrates results from one method with the use of another method. In our case, in-class observation will add information about the learning process and will qualify the scores and statistics.
Development results from one method which shapes subsequent methods or steps in the research process (e.g. partial results from the pre-program measures might suggest that other assessments should be incorporated).
Initiation stimulates new research questions or challenges results obtained through one method. In the example provided by Greene et al. in-depth interviews with teachers and principals will provide new insights on how the program has been perceived and valued across sites.
Expansion provides richness and detail to the study exploring specific features of each method (e.g. integration of procedures mentioned above will expand the breadth of the study and likely enlighten the more general debate on social change, social justice, and equity in Brazil and the role of the public and private sector in this process).
These five purposes were developed by Bryman later on in 2006 and 18 more detailed rationales emerged from this development.
Campbell, D.T. & Fiske, D.W. (1959). Convergent and discriminant validation by the multitrait-multimethod matrix. Psychological Bulletin, 56: 81-105.
Denzin, N.K. 1970. The research act. Chicago: Aldine Publishing.
Greene, Jennifer C., Caracelli, Valerie J. and Graham, Wendy F. 1989. Toward a conceptual framework for mixed-method evaluation design. Educational Evaluation and Policy Analysis, 11(3), pp. 255-74.
Bryman, A. 2006. Integrating Quantitative and Qualitative Research: How is it Done? in Qualitative Research 6 (1) pp.97-113.