Sentence:  One recent attempt to combine both forms of data collection ... was based on a parallel methods approach, in which the results of two similar but separately located studies were triangulated. <WSD>"Triangulation</WSD>" entails overlapping the results at several points to enhance reliability. ... Other documented research has attempted to gain a broader view through the <WSD>triangulation</WSD> of two sets of data (quantitative and qualitative) on the same question, taken from the same respondents in a single study. 
Meaning of the word marked with <WSD> tags:  The use of three (or more) researchers to interview the same people or to evaluate the same evidence to reduce the impact of individual bias.