A student conducted 21 DN? project as a retrospective program evaluation over4 years to evaluate the impact of a Six-Sigma team on the incidence of hospital acquired DVT in surgical patients. The student has incidence of DVT tracked by month over the 4-year period, the date of the incident, the number of days between each event, and the number of surgical procedures during each month. With these data, the student could do either a control chart or a simple run chart to show improvement