A case-control study is characterized by all of the following EXCEPT: - CORRECT ANSWERS - Cases with the disease are compared to controls without the disease Of 2872 persons who had received radiation treatment in childhood because of enlarged thymus, cancer of the thyroid developed in 24 and benign thyroid tumor developed in 52. A comparison group consisted of 5055 children who had received no such treatment (brothers and sisters of those children who had received radiation treatment). During the follow up period, none of the comparison group developed thyroid cancer, but benign thyroid tumors developed in 6. Calculate the relative risk for benign thyroid tumors: - CORRECT ANSWERS a/(a+b) / c/(c+d) = 15,25 In a small pilot study, 12 women with endometrial cancer (cancer of the uterus) and 12 women with no apparent disease were contacted and asked whether they had ever used estrogen. Each woman with cancer was matched by age, race, weight and parity to a woman without disease. What kind of study is this? - CORRECT ANSWERS - case-control The purpose of a double-blind or double-masked study is to: - CORRECT ANSWERS - avoid observer and subject bias In a study of 500 cases of a disease and 500 controls, the suspected etiological factor is found in 400 of the cases and 100 of the controls. The absolute risk (incidence) of disease in persons with the factor is: - CORRECT ANSWERS - cannot be computed from data given (You dont have outcome or incidence, so you cant calculate the absolute risk (incidence rate)) Epidemic refers to: - CORRECT ANSWERS - the occurrence of illnesses of similar nature clearly in excess of the normal expectation for that population at that time Communities P and Q have equal age-adjusted mortality rates. Community P has a lower crude mortality rate than Q. One may conclude that: - CORRECT ANSWERS - P has a younger population than Q All of the following statements about multiple tests carried out in series are true EXCEPT: - CORRECT ANSWERS - the specificity is lower than for tests carried out in parallel Parallel: inc sensitivity, dec specificity Series: dec sensitivity, inc specificity Mormons and Seventh-Day Adventists have lower-than-average age-adjusted death rates. The avoidance of alcohol and tobacco and the adherence to a healthful diet by members of these groups are factors: - CORRECT ANSWERS - associated with the lower mortality rates but may not be causal factors In a prospective study of a disease, the cohort originally selected consisted of: - CORRECT ANSWERS - persons with the factor under investigation A study is conducted in which the rate of cigarette smoking and the prevalence of tuberculosis are assessed in the same population at the same time. Both are found to be high, and the conclusion is drawn that cigarette smoking is causally related to tuberculosis. Based on this study only, all of the following are true statements regarding this conclusion EXCEPT: - CORRECT ANSWERS - it may be incorrect due to the ecologic fallacy Multiple disease outcomes can be studied, but only the risk factors defined and measured at the beginning of the study can be assessed. - CORRECT ANSWERS - prospective cohort study Only one outcome may be studied, but many risk factors or exposures may be assessed. - CORRECT ANSWERS - case-control study All of the following should be true of a disease for which screening is planned EXCEPT - CORRECT ANSWERS - the disease should be rare During a 3-month period, 9 cases of Hantavirus pulmonary syndrome are reported, and 3 of the cases die. Which of the following calculations would be 33%? - CORRECT ANSWERS - the case fatality ratio In a diabetes detection program the screening level for blood sugar test A is set at 160 mg/100 ml and for test B at 130mg/100mg. This would mean that: - CORRECT ANSWERS - the specificity of a test A is greater than that of test B Overweight was recognized as a risk factor for a disease X (RR=4,0). The proportion of obese individuals in the population of interest is 50%. What is P AF (population attributable fraction) for smoking in the disease X - CORRECT ANSWERS - cannot be determined on the basis of provided data