Statistical evidence played an important role in the murder trial of kristen gilbert, a nurse who was accused of murdering hospital patients by giving them fatal doses of a heart stimulant. hospital records for an eighteen-month period indicated that of the 257 eight-hour shifts that gilbert worked, a patient died on 40 of those shifts (15.6%). but during the 1384 eight-hour shifts that gilbert did not work, a patient died on only 34 of those shifts (2.5%). a. identify the observational units in this study. b. identify the two variables mentioned in the preceding paragraph. classify each as categorical or quantitative