Many students have difficulty mastering the demands of medical courses. Applying the Triads method, the present research compares the validity of three self-reported methods that measure self-study hours in a medical course. Thirty randomly selected students participated in this study. Three surveys were developed: continuous weekly records (WR) and two end-course retrospective self-reported surveys, AR (asking average hours/week during academic year) and FR (asking study frequency throughout academic year and mean hours of studying on a given day). Validity coefficients (VCs), which measure the correlation between observed and "true" self-study, were estimated using the Triads method. The estimated VC was 0.86, 0.94 and 0.87 for WR, FR and AR, respectively. Therefore, given the demands of WR and, since FR showed more accuracy than AR, we propose a novel method, FR, to retrospectively estimate self-study in a medical course.