Mixed Methods Research

Qualitative and Quantitative Research

There is no agreement on a precise distinction between quantitative and qualitative research; both include quite diverse approaches and methods, and there are multiple differences between the two, none of which are entirely definitive. The simplest (and common) distinction, that quantitative [Page 1070]research involves numbers and qualitative involves only words, is clearly inadequate; both fields use numbers (although quantitative research relies much more heavily on them), and the numbers/words distinction fails to capture other commonly invoked differences between these approaches, including the use of artificial versus natural settings, a primary reliance on deductive versus inductive strategies, and a positivist versus constructivist epistemology. None of these distinctions adequately capture the diversity of strategies within each approach, and none definitively distinguish the two approaches.

However, the distinction is extremely meaningful to researchers in both communities and was central to the development of mixed methods research. A different way of distinguishing the two approaches, in terms of their strategy for explanation, was proposed by the evaluation researcher Lawrence Mohr and may be helpful in clarifying the differences. Mohr identified two types of explanation, which he termed variance theory and process theory. Others had earlier presented similar distinctions but had not developed them as systematically. Variance theory is based on the concept of a variable, a property of something that can vary, and can be measured or categorized. This concept is fundamental to quantitative research; essentially, all such research involves the creation and correlation of different variables, or comparison of the values of particular variables, across persons or other units of analysis. The use of variables allows precision in counting or measuring social phenomena, determining differences between individuals or groups on particular variables, and identifying relationships between variables.

Qualitative research, in contrast, makes very little use of variance theory; although some qualitative researchers use the term variable, they do not employ it in the same way as quantitative researchers. Instead, they focus on describing the phenomena studied (behavior, meaning, experience, and social organization) in a specific context and understanding the processes (physical or mental) that connect these phenomena, thus being labeled as process theory by Mohr.

These differences are fundamental to understanding the explicit development of mixed methods research because conflicts between advocates for the two approaches were intrinsic to this development and because the complementarity between quantitative and qualitative research, in terms of their strengths and limitations, provides the main rationale for combining the two approaches. Quantitative research is better at answering “what” and “how much” questions, such as, “Did this educational program make a difference in academic achievement for these students, and how much of a difference?” Qualitative research is better at answering “how” and “why” questions, such as, “How was the program experienced and understood by participants, and how did this shape their responses; how was it influenced by the particular context in which it occurred; and how and why did it achieve these results?” The answers to both types of questions are important for policy and practice, and a mixed methods study is much more capable of answering both.

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