“Triangulation” is a term that is frequently mentioned in publications of qualitative studies. Typically, scholars mention “triangulation” in discussions to do with how the “quality” or “validity” of a study might be assured (e.g., Seale, 1999; Tracy, 2010). Where did the term “triangulation” come from, and how did it come to be used in qualitative inquiry?
Pelto (2017, p. 241) presents an intriguing history of triangulation which sources the concept from trigonometry, by way of surveying and mapping, through it’s use by quantitative researchers, to it’s redefinition and application in qualitative inquiry. According to Pelto, in the 1950s researchers began to use “triangulation” (defined as using more than one research method) as “an approach to assessing the validity and reliability of data-gathering methods in the social and behavioural sciences” (p. 242). Pelto (2017, pp. 242-243) explains that Campbell and Fiske (1959) published one of the first papers to advocate for “methodological triangulation” (Campbell & Fiske, 1959, p. 101) as an alternative approach to “the single operationalism now dominant in psychology” (p. 101) (italics in original).
The aforementioned paper by Campbell and Fiske (1959) is mentioned by Norman Denzin (1978) as a source of inspiration for his book The Research Act: A Theoretical Introduction to Sociological Methods. In this book, Norman Denzin (1978) argues for an approach to naturalistic inquiry that examines research problems from multiple perspectives – including those of “multiple observers, theories, methods, and data sources”, with the intent of overcoming the “intrinsic bias that comes from single-method, single-observer, single-theory studies” (p. 307). Denzin argued strongly for interactionist research that used multiple approaches, commenting that
multiple methods should be used in every investigation, since no method is ever free of rival causal factors (and thus leads to completely sound causal propositions), can ever completely satisfy the demands of interaction theory, or can ever completely reveal all the relevant features of empirical reality necessary for testing or developing a theory (p. 28).
In this text, Denzin clearly situates his work in the field of sociology, employing principles of symbolic interactionist theory. In the decades since publication of this book, it is Denzin’s text that is a frequent citation for “triangulation” as an indicator for “quality” in qualitative inquiry. The idea that the aim of “convergence” is the focus of triangulation (cf. Tracy, 2010, p. 843) has also proliferated. In reading Denzin’s account (1978), he insists that by using multiple forms of triangulation in a study, sociologists might develop propositions that permit discovery and verification (pp. 32-33). Writing from a symbolic interactionist perspective, Denzin argued in his 1978 text that “triangulation, or the use of multiple methods, is a plan of action that will raise sociologists above the personalistic biases that stem from single methodologies” (p. 294). In an effort to unite the interrelated enterprises of sociology – theory, research, and substantive interest (p. 3), Denzin outlined the ways in which qualitative researchers can use “triangulation” of method, investigator, theory and data in naturalistic inquiry (p. 294). Denzin asserted that researchers could use multiple forms of triangulation in a study. These included:
- Data triangulation of (1) time, (2) space, and (3) person, with person analysis of multiple levels: (a) aggregate, (b) interactive, and (c) collectivity (p. 295). By triangulating data sources, researchers “go to as many concrete situations as possible in forming the observational base” (p. 101). Denzin notes that “theoretical sampling” is an example of data triangulation (p. 295):.
- Methodological triangulation, or the use of multiple methods (both “within-method” and; “between-method” p. 295) in order to to “better unravel the processes under study” (p. 102).
- Theory or perspective triangulation refers to the ways in which researchers might compare participants’ own accounts with “alternative theoretical schemes” (p. 102) in order to use multiple, rather than single perspectives to examine a topic. According to Denzin, “the goals is to form a theory that rings true at the subjects’ level, while conforming with accepted sociological rules concerning how a theory should be grounded” (p. 102).
- Investigator triangulation, in which involvement of multiple observers was used to attempt “to secure as many differing views as possible on the behavior in question” (p. 102).
Denzin concludes the book with a discussion of the problems with multiple-triangulated investigations (pp. 305-306), including
- “locating a common unit of observation against which various theories can be applied” (p. 305).
- “restrictions of time and money” (p. 306).
- “serious consideration of a problem will often reveal that what appears to be unique is in reality a special case of a problem previously treated by standard theories and methods” (p. 306); and
- “inaccessibility of critical areas, types, or levels of data” (p. 306).
Sandra Mathison (1988) has since outlined an alternative way of conceptualizing triangulation, suggesting that there are three possible outcomes of using the approaches to triangulation discussed by Denzin (1978):
- Convergence – “data from different sources, methods, investigators, and so on will produce evidence that will result in a single proposition about some social phenome men” (p. 15);
- Inconsistency – “multiple sources, methods, and so on….[generate] range of perspectives or data that do not confirm a single proposition about a social phenomenon” (p. 15); and
- Contradiction – the use of multiple methods results “in opposing views of the social phenomenon studies” (p. 15).
When a research study yields not convergence on a single explanation, but data that supports inconsistent or contradictory explanations, Mathison (1988, p. 17) asserts that the researchers need to “make sense of what we find.” In Mathison’s view, this moves “the focus on triangulation away from a technological solution for ensuring validity and places the responsibility with the researcher for the construction of plausible explanation about the phenomena being studied” (p. 17).
It is important for researchers using qualitative designs and methods in their research to consider the limitations and benefits of their choice of methods. Qualitative researchers also need to consider what “quality” means for a study conducted using a particular research design (i.e., quality criteria for autoethnography, narrative inquiry, ethnography, case study etc. may differ). Articulating how one approaches the issue of quality is complicated by the many approaches used by qualitative researchers (e.g., Freeman, deMarrais, Preissle, Roulston, & St. Pierre, 2007), and whether or not a researcher believes it is even possible to have common criteria for assessment of quality (Tracy, 2010). Although “triangulation” may be one strategy used in a study, by examining the historical roots of triangulation, one can make a more informed decision about whether or not this concept is both useful and applicable for any particular study.
Campbell, D. T., & Fiske, D. W. (1959). Convergent and discriminant validation by the multitrait-multimethod matrix. Psychological Bulletin, 56(2), 81-105. doi:10.1037/h0046016
Denzin, N. K. (1978). The research act: A theoretical introduction to sociological methods (2nd ed.). New York: McGraw-Hill.
Freeman, M., deMarrais, K., Preissle, J., Roulston, K., & St. Pierre, E. A. (2007). Standards of Evidence in Qualitative Research: An Incitement to Discourse. Educational Researcher, 36(1), 25-32. doi:10.3102/0013189×06298009
Mathison, S. (1988). Why triangulate? Educational Researcher, 17(2), 13-17.
Pelto, P. J. (2017). Mixed methods in ethnographic research: Historical perspectives. New York & London: Routledge.
Seale, C. (1999). The quality of qualitative research. London: Sage.
Tracy, S. J. (2010). Qualitative quality: Eight “Big-Tent” criteria for excellent qualitative research. Qualitative Inquiry, 16(10), 837-851. doi:10.1177/1077800410383121