The Validity Issue in Mixed Research

TLDR

Validity is well established in quantitative research, debated with diverse typologies in qualitative research, and remains an emerging issue in mixed‑methods studies. The authors contend that because mixed research combines complementary strengths and nonoverlapping weaknesses, assessing validity—termed legitimation—is particularly complex. They summarize Tashakkori and Teddlie’s inference‑quality evaluation criteria and outline nine legitimation types to guide assessment in mixed research. Although any legitimation framework will be incomplete, the authors highlight several legitimation types that arise when integrating quantitative and qualitative inferences into meta‑inferences.

Abstract

In quantitative research, the importance of validity has been long accepted. In qualitative research, discussions of validity have been more contentious and different typologies and terms have been produced. In mixed methods research, wherein quantitative and qualitative approaches are combined, discussions about “validity” issues are in their infancy. We argue that because mixed research involves combining complementary strengths and nonoverlapping weaknesses of quantitative and qualitative research, assessing the validity of findings is particularly complex; we call this the problem of integration. We recommend that validity in mixed research be termed legitimation in order to use a bilingual nomenclature. Tashakkori and Teddlie’s (2003, 2006) evaluation criteria frameworks involving the concept of inference quality are summarized. Although providing a framework for assessing legitimation in mixed research always will be incomplete, it is important to address several legitimation types that come to the fore as a result of combining inferences from the quantitative and qualitative components of the study into the formation of meta-inferences. Nine types of legitimation are described here in order to continue this emerging and important dialogue among researchers and methodologists.