presents a hypothetical example comparing survival rates in victims by evacuation method.

TABLE 19.11 Data for Exercise 19.6. Survival following motor vehicle accidents by evacuation method and seriousness of accident. Data are hypothetical.

Data from Oppe, S., & De Charro, F. T. (2001). The effect of medical care by a helicopter trauma team on the probability of survival and the quality of life of hospitalized victims. Accident Analysis & Prevention, 33(1), 132.

(a) Table 19.11A cross-tabulates the data for all accidents. Calculate the crude relative risk of death associated with helicopter evacuation.

(b) Data stratified by the seriousness of the accident are reported in Table 19.11B and 19.11C. Calculate these strata-specific relative risks.

(c) How do you explain the discrepancy between the crude results and strata-specific results?

(d) Calculate the Mantel–Haenszel adjusted summary relative risk for helicopter evaluation and death while adjusting for the seriousness of the accident.