4. This problem is an extension of the biologic interaction in class exercise from Nov 11/13.

Formula 1. Biologic Interaction Risk = RiskAB – RiskA – RiskB + RiskU

Formula 2. Biologic Interaction Independence = (RRA-1)  + (RRB-1) = (RRAB-1)

4A. Using the risk of death among the exposure categories (Table 3), calculate the odds of death for each of the 4 categories. Fill in Table 5 above.

Using the formulas for Biologic Interaction, calculate the proportion of risk/odds in the jointly exposed (HIV and Alcohol Abuse) due to biologic interaction three ways (4B, 4C, 4D). Use formula 1 for 4C and formula 2 for 4D but substitute odds for risk.

4B. Using risk

4C. Using odds

4D. Using odds ratios

4E. How does the calculation in part 4C compare to part 4D?