Int. J. Environ. Res. Public Health 2009, 6 2816 Table 1. Frequency distribution (n, %) of demographics of cohort members n = 167. Demographics Age <30 y/o 30-44 y/o >44 y/o Sex Male Female Education level High school College Marital status Unmarried Married Religious belief Religious Unreligious Workplace Acute ward Chronic ward Rehabilitation ward Degree of worry about violence Not at all A little worried Moderate worried Very and extremely worried n % 42 78 47 62 105 73 94 78 89 53 114 90 57 20 23 94 32 18 25 47 28 37 63 44 56 47 53 32 68 54 34 12 14 56 19 11 Table 2 shows the frequency distribution of the 971 violent events reported, and the incidence rate of PV, VA, BM, and SH, 1.7, 3.7, 0.2, and 0.3 per staff-year, respectively. No racial harassment was reported in this study. Because only seven cases dropped out as early 2–3 months as the study began and no violence were reported by them, we simply neglected their contributions to calculate the incidence. For example, to get the incidence of total violence, the number of total violence reported is divided by the number of staff completed the study and the follow-up time, 1 year, that is, incidence of total violence = 971/(167 × 1) = 5.8 per staff-year (Table 2). If we considered the drop-out cases, three of them dropped out on 31/10/2005, and four dropped out on 30/11/2005, then the incidence of total violence would be gained by 971/[(167 × 1) + 3 × (2/12) + 4 × (3/12)] = 5.76, only a little less than 5.8. Table 2. Incidences of types of violence, from 1/9/2005 to 31/8/2006. Types of violence Physical violence Verbal abuse Bullying and mobbing Sexual harassment Racial harassment Total n 284 611 33 43 0 971 % 29.6 62.9 3.1 4.4 0 100 Incidence (per staff year) 1.7 3.7 0.2 0.3 0 5.8