The demographics of physics education research

Is physics education research based on a representative sample of students? To answer this question we skimmed physics education research papers from three journals for the years 1970 - 2015 looking for the number of research subjects, the course the subjects were enrolled in, and the institution where the research was conducted. We then compared the demographics of our research population to those of all students taking physics in the United States. Our results suggest that research subjects as a whole are better prepared mathematically and are less diverse than the overall physics student population.