Sample selection

This research was conducted on medical college students between October and November 2018 in Shandong province, China. According to the 2018 National Bureau of Statistics data, this region has a population exceeding 100 million, which makes it the second largest in China. The following sample size calculation formula was employed: N = uα/22×π(1-π)δ2(π: expected prevalence)⁵⁹. According to previous studies, the proportion of medical students who scored above 24 on Beck's SI scale was about 12.75%⁶⁰, in this research, π = 0.128, α = 0.05, uα/2 = 1.96, and δ = 0.0128. By calculating for the 2,617 samples needed, the failure and rejection of interviews were fully taken into account in the research center. The final sample size of the study was 2800.

This study used a cross-sectional design and a multi-stage cluster sampling technique to select medical undergraduates from two medical schools. It covered all 12 medical majors, including clinical medicine, preventive medicine, pharmacy, stomatology, nursing, and rehabilitation medicine. For each major, we selected all grades from the first to the fourth or the fifth, in each of which, a complete class was chosen to partake in the survey. Overall, 2598 respondents answered the questionnaire, including 1162 boys (44.7%) and 1436 girls (55.3%), with an average age of 20.42 years. They were not compensated with academic credits or anything else. Finally, 2800 questionnaires were distributed, with a response rate of 94.5%, and 2646 valid questionnaires were collected.