Document YDkLYQoRDJyMv3N8wa9ELjqjk

Page 3476 1 In this case we are talking about a cohort 2 of candy eaters compared to a group of noncandy 3 eaters. That would be a cohort study. 4 We follow them and find out how many of them 5 develop stomach cancer in this group. That is what we 6 call a cohort study. 7 There is another study designed in 8 epidemiology, what we call case control study. 9 Now, let me give you an example. Again, 10 using candies as an example. 11 We can look at stomach cancer patients and 12 find out how many of them were candy eaters. 13 Let's say out of 100, we notice that 90 of 14 them ate candies and then we scratch our head and say 15 is that high or low? 16 Is there a relationship between candies and 17 stomach cancer? 18 Q Let me stop you right there. 19 Why don't you know at that point whether 20 that is high or low? 21 A You need a control group.