“One important way to strengthen a study design is through triangulation, or the combination of methodologies in the study of the same phenomena or programs. This can mean using several kinds of methods or data, including using both quantitative and qualitative approaches. Denzin (1978b) has identified four basic types of triangulation: (1) data triangulation - the use of a variety of data sources in a study; (2) investigator triangulation-the use of several different researchers or evaluators; (3) theory triangulation-the use of multiple perspectives to interpret a single set of data; and (4) methodological triangulation-the use of multiple methods to study a single problem or program.

The term triangulation is taken from land surveying. Knowing a single landmark only locates you somewhere along a line in a direction from the landmark, whereas with two landmarks you can take bearings in two directions and locate yourself at their intersection (Fielding and Fielding, 1986: 23). The term triangulation also works metaphorically to call to mind the world's strongest geometric shape-the triangle (e.g., the form used to construct geodesic domes a la Buckminster Fuller).”

(Patton, 1990, sid. 187)