1. Chance Is the association causal? RR = 7 Detectives in the Classroom – Investigation 3-3: Chance

2. Hypotheses 2 Is there an association? 4 What should be done to prevent the disease? 5 Did the prevention strategy work? Where are we and where are we going? Detectives in the Classroom – Investigation 3-3: Chance 1 How is this disease distributed? What’s my hypothesis? Did the exposure and the disease turn up together? 3 Is the association causal? Why did the exposure and the disease turn up together?

3. What is a cause? If an exposure causes an outcome, how can people be in cell b of a 2 x 2 table? If an exposure causes an outcome, how can people be in cell c of a 2 x 2 table? How does this apply to the “… cigarette smoking causes lung cancer …” label? Review Detectives in the Classroom – Investigation 3-3: Chance

4. 1.Cause 2.Chance 3. 4. 5. Review Detectives in the Classroom – Investigation 3-3: Chance

5. Epi Talk All the people in a particular group. Population Review Detectives in the Classroom – Investigation 3-3: Chance

6. Epi Talk A selection of people from a population. Sample Epi Talk Detectives in the Classroom – Investigation 3-3: Chance

7. Epi Talk Review Inference Process of predicting from what is observed in a sample to what is not observed in a population. To generalize back to the source population. Detectives in the Classroom – Investigation 3-3: Chance

8. Sample Population Process of predicting from what is observed to what is not observed. Observed Not Observed Review Detectives in the Classroom – Investigation 3-3: Chance

9. Population Deck of 100 cards Detectives in the Classroom – Investigation 3-3: Chance

10. Population a 25 cards b c d Detectives in the Classroom – Investigation 3-3: Chance

11. Population = a 25 cards bc d = ab cd M&M’s No M&M’s Flu No Flu Detectives in the Classroom – Investigation 3-3: Chance

12. = Population a 25 cards bc d = M&M’s No M&M’s Flu No Flu 25 50 Total Population Detectives in the Classroom – Investigation 3-3: Chance

13. Risk Epi Talk A measure of how often an event occurs in a defined group of people in a defined period of time. The likelihood of developing a disease. Review Detectives in the Classroom – Investigation 3-3: Chance

14. = Population = M&M’s No M&M’s Flu No Flu 25 50 Total = 25 50 Total M&M’s No M&M’s Flu No Flu a 25 cards bc d Population Detectives in the Classroom – Investigation 3-3: Chance

15. = Population = 25 50 Total a 25 cards bc d Risk 25 / 50 or 50% M&M’s No M&M’s Flu No Flu Population Detectives in the Classroom – Investigation 3-3: Chance

16. Epi Talk A way of showing the relationship between two risks. Calculated by dividing the risk of an outcome in one group by the risk of the outcome in another group. Tells us the number of times one risk is larger or smaller than another. Relative Risk Review Detectives in the Classroom – Investigation 3-3: Chance

17. Sample Detectives in the Classroom – Investigation 3-3: Chance 1

18. = Population a 25 cards bc d = 25 50 Total M&M’s No M&M’s Flu No Flu RiskRelative Risk 25 / 50 or 50 % 50 % / 50% = 1 Population Detectives in the Classroom – Investigation 3-3: Chance 1 The risk of getting the flu is no more likely among those who ate M&M’s than among those who did not eat M&M’s.

19. Epi Teams Detectives in the Classroom – Investigation 3-3: Chance

20. Population 25 cards Detectives in the Classroom – Investigation 3-3: Chance

21. Epi Talk To occur accidentally. To occur without design. Chance Epi Talk A coincidence. Detectives in the Classroom – Investigation 3-3: Chance

22. Chance Detectives in the Classroom – Investigation 3-3: Chance

23. Chance Detectives in the Classroom – Investigation 3-3: Chance

24. Population Sample b Sample of 20 cards 25 cards Detectives in the Classroom – Investigation 3-3: Chance

25. Population Sample b Sample of 20 cards 25 cards 10 Total M&M’s No M&M’s Flu No Flu 55 55 Sample Detectives in the Classroom – Investigation 3-3: Chance

26. Population Sample b Sample of 20 cards 25 cards 10 Total M&M’s No M&M’s Flu No Flu 55 55 Risk 5 / 10 or 50 % Sample Detectives in the Classroom – Investigation 3-3: Chance

27. Sample Detectives in the Classroom – Investigation 3-3: Chance 2

28. Population Sample b Sample of 20 cards 25 cards 10 Total M&M’s No M&M’s Flu No Flu 55 55 Risk 5 / 10 or 50 % 50 % / 50% = 1 Relative Risk Sample 2 Detectives in the Classroom – Investigation 3-3: Chance The risk of getting the flu is no more likely among those who ate M&Ms than among those who did not eat M&Ms.

29. b Sample of 20 cards Total M&M’s No M&M’s Flu No Flu Risk 5 / 10 = 50 % 50 % / 50% = 1 Relative Risk By Chance CDC Sample Detectives in the Classroom – Investigation 3-3: Chance

30. Sample Detectives in the Classroom – Investigation 3-3: Chance 3

31. b Sample of 20 cards Total M&M’s No M&M’s Flu No Flu Risk 5 / 10 = 50 % 50 % / 50% = 1 Relative Risk By Chance CDC By Chance Sample 3 Detectives in the Classroom – Investigation 3-3: Chance

32. 10 Total M&M’s No M&M’s Flu No Flu 55 55 Risk 5 / 10 or 50 % 50 % / 50% = 1 Relative Risk By Chance How many students picked a sample with 5 people in each cell? Chance Detectives in the Classroom – Investigation 3-3: Chance

33. Relative Risks Greater than 1 Chance Less than 1 Detectives in the Classroom – Investigation 3-3: Chance

34. Chance Study Links Eating M&M’s To Increased Risk of Flu Detectives in the Classroom – Investigation 3-3: Chance

35. Relative Risks Chance Greater than 1Less than 1 Detectives in the Classroom – Investigation 3-3: Chance

36. Chance Study Links Eating M&M’s To Decreased Risk of Flu Detectives in the Classroom – Investigation 3-3: Chance

37. Relative Risks Chance Greater than 1Less than 1 1 By Chance 25 cards Detectives in the Classroom – Investigation 3-3: Chance

38. Sample Detectives in the Classroom – Investigation 3-3: Chance 4

39. b Sample of 20 cards Total M&M’s No M&M’s Flu No Flu Risk 5 / 10 = 50 % 50 % / 50% = 1 Relative Risk Different Sample Sizes Detectives in the Classroom – Investigation 3-3: Chance 50

40. Sample Detectives in the Classroom – Investigation 3-3: Chance 5

41. b Sample of 20 cards Total M&M’s No M&M’s Flu No Flu Risk 5 / 10 = 50 % 50 % / 50% = 1 Relative Risk Different Sample Sizes Detectives in the Classroom – Investigation 3-3: Chance 75

42. Sample Detectives in the Classroom – Investigation 3-3: Chance 6

43. b Sample of 20 cards Total M&M’s No M&M’s Flu No Flu Risk 5 / 10 = 50 % 50 % / 50% = 1 Relative Risk Different Sample Sizes Detectives in the Classroom – Investigation 3-3: Chance 99

44. Sample Detectives in the Classroom – Investigation 3-3: Chance 7

45. Explanations for Finding an Association Why would an exposure and an outcome turn up together? 1.Cause 2.Chance 3. 4. 5. Study Links Eating M&M’s To Decreased Risk of Flu Detectives in the Classroom – Investigation 3-3: Chance

46. Could the association have occurred by chance? Explanations for Finding an Association RR = 7 Detectives in the Classroom – Investigation 3-3: Chance

47. CDC Investigation 3-3 has ended. Chance Detectives in the Classroom – Investigation 3-3: Chance