# Calculate relative risk of myocardial infarction for those smoking…

1. A case-control study of association between myocardial infarction and smoking shows these results: Non-smoker (unexposed) Smokers (exposed) No. of packs/ day 0.5 1 2 cases 31 9 39 18 controls 2,706 710 1,825 605 Calculate relative risk of myocardial infarction for those smoking (non-smokers as the reference group) a. 0.5 pack per day b. 1 pack per day c. 2 packs per day 2. A study about association between regular physical activity and colon cancer reported that the incidence rate of colon cancer among people engaged in regular physical activity was 30 per 100,000 person-years of follow-up, whereas the rate among people who did not engage in regular activity was 45 per 100,000 person-years of follow-up. a. Compute the incidence rate ratio of colon cancer for people who are physically active versus people who are not. b. State in words your interpretation of this measure. c. Compute the incidence rate difference of colon cancer for people who are physically active versus people who are not. d. State in words your interpretation of this measure. e. If there were no association between regular physical activity and colon cancer, what would be the values of the incidence rate ratio and incidence rate difference? 3. A serologic test is being devised to detect a hypothetical chronic disease. Three hundred individuals were referred to a laboratory for testing. One hundred diagnosed cases were among the 300. A serologic test yielded 200 positives, of which one-fourth were true positives. Calculate the sensitivity, specificity, and predictive values of this test. 4. A physical examination was used to detect for cervical cancer in 2,500 women who were diagnosed with cervical cancer (cases), and in 5,000 age- and race- matched control women who were healthy. The results of the physical examination were positive in 1,800 cases and in 800 control women. a) Place these data in an appropriated table. b) Calculate sensitivity of the physical examination. c) Calculate specificity of the physical examination. d) Calculate positive predictive value of the physical examination.