We construe the term “empirical educational research” broadly to include experimental and quasi-experimental quantitative studies, qualitative studies of various kinds, and design experiments. To be classified as “empirical,” a study must make use of data/evidence from observation or experiment. To be “research,” the data must be gathered and analyzed systematically. Empirical educational research is reported in peer-reviewed journals after being thoroughly vetted by others engaged in similar inquiry.
Be wary of individual teachers’ anecdotal reports of “I taught it this way,” usually found in practitioner’s journals and magazines. These personal descriptions of and reflection on practice are not the same as systematic case studies. Your goal is to determine what research-based knowledge is available to inform the thinking of teachers as they take on the selected subject matter. Keep your eye on research journals (especially those listed on this page). Occasionally there are useful empirical reports in practitioners’ journals, but that is less likely.