Length of stay measure. The number of calendar days (LOS calendar) was most frequently used to determine length of stay. While these data are easy to obtain from existing documents, this method can lead to overestimation (Marik & Hedman, 2000). Marik and Hedman suggest estimating LOS from the number of midnight bed occupancy days or total hours.
Nurse staffing measure. Nurse staffing variables measured in the included studies were the ratio of RNs to patients, hours per patient day, staff hours, the ratio of RNs to other nursing staff, and RN qualification. These variables are commonly found in the research literature examining the impact of nurse staffing on patient mortality, patient falls, medical errors, or other patient outcomes. Each of these variables provides different information about how nurses are assigned to care for their patients and work with each another. Using RN-to-patient ratios, hours per patient day and staff hours provides information about the appropriate utilization of nurse staffing in terms of the number of nursing staff per patient day. Skill mix (expressed in the ratio of RNs to other nursing staff) provides information about the appropriate utilization of nurse staffing in terms of workload shared between RNs and non-licensed nurses. RN qualification (expressed in the ratio of total number of RN years of experience to the total number of staff) indicates the efficiency of using RNs with more years of nursing experience. Theoretically, RNs with more years of nursing experience are expected to provide higher quality care and thus positively affect patient outcomes.