Fig. 1

Sampling process flow chart. *The number in brackets is the total number of students in each university or major. **University 1 indicates Hebei Medical University; University 2 indicates North China University of Science and Technology; University 3 indicates Health Science Center of Hebei University; University 4 indicates Hebei University of Chinese Medicine; University 5 indicates Chengde Medical University; University 6 indicates Hebei North University. ***Clinical-related majors includes Clinical medical; Stomatology; Anesthesiology; Psychologic medicine; Chinese medicine and related majors includes Chinese and western integrative medicine; Chinese medicine; Other medical-related majors includes Pharmacy; Medical imaging technology; Laboratory medicine; Medical imageology; Forensic medicine; Rehabilitation medicine; Hygienic managerialics