Chapter 8 Review Questions (Key)

§8.1 Introduction

  1. "Exposure"
  2. "Disease"
  3. True
  4. A positive association indicates that the exposed group has a higher incidence of disease than the non-exposed group. A negative association indicates that the exposed group has a lower  incidence of disease than the non-exposed group.
  5. False. Not all associations are causal.
  6. False. Absolute comparisons are made by subtraction. 
  7. True 
  8. False.
  9. True. 
  10. risk difference (RD)
  11. risk ratio (RR)
  12. RD = (50 per 100) - (35 per 100) = 15 per 100. This implies that, if the non-exposed group had been exposed, there would be 15 additional cases per 100 individuals.
  13. RR = (50 per 100) ÷ (35 per 100)= 1.43. This implies the exposed group has 1.43 times the risk of the non-exposed group (equivalent to a 43% increase in risk, relatively speaking). 
  14. RR
  15. No 
  16. 40% 
  17. False
  18. True
  19. The baseline RD is 0. 
  20. It changes the sign of the risk difference from positive to negative or vice versa.
  21. This suggests there are 54.3 fewer deaths per 10,000 person-years with improved physical fitness (in this particular population).
  22. The baseline RR is 1. 
  23. It changes to risk ratio to it's reciprocal. For example, an RR of 2 becomes 1/2 = 0.5.
  24. The exposure increases risk by 0.85 or 85%.
  25. AFe
  26. AFp
  27. Because there are multiple ways to prevent any given case (see causal pie model).
  28. The AFp applies to the entire population. The AFe applies only to exposed cases.
  29. a = RD, b = RR, c = AF