Odds Ratio Exercise

An outbreak of Listeria occurred at the Canadian National Exhibition. In a case-control study, investigators found that 21 of 30 people that got Listeria ate the featured dish, the 5-pound hot dog. The investigators compared with a sex- and age-matched group of 60 people, finding 4 people ate the 5-pound hot dog.

	Listeria	No listeria
Yes, ate 5-pound hot dog	21	4
No, didn't eat 5-pound hot dog	9	56

• Using the above table, calculate:
  1. The odds of being exposed to/eating the 5-pound hot dog (Listeria)
  2. The odds of being exposed to/eating the 5-pound hot dog (no Listeria)
  3. The odds ratio
  4. The relative risk (using the conversion formula)
• Interpret in words:
  1. The odds ratio
  2. The relative risk converted
• What is the main reason why the relative risk (converted) and odds ratio are so different?