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unit 6 answes

unit 6 answes - Unit 6 Questions and Answers Epidemiology...

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Unit 6 Questions and Answers Epidemiology 6000 One concept we did not cover is that of a “dose-response”.  This means that as the exposure  intensity (or amount) increases, the risk increases or decreases with it.  An example would be  number of cigarettes smoked per day.  If we group number of cigarettes smoked per day into 1-9,  10-19, 20-29, 30-39, 40+, we would expect that the risk of lung cancer would look something like  this: # cigarettes/day Risk of Lung Cancer (OR)  0 (non-smokers) 1.0 (reference group) 1-9 1.8 10-19 2.6 20-29 3.9 30-39 5.8 40+ 7.2 Notice how the OR increases with increasing exposure.  We call this a “dose-response effect”  and we can test the  p -value associated with this increase.  If the  p -value is statistically significant,  we say that the  p  for trend is significant (p<0.05 usually).  There are a couple of references to  “dose-response” in the questions below. Answer True or False for Questions 1-2. Question 1 The p -value is a measure of the probability that the estimated association could be due to chance (when in fact there is no association at the population level) A. True B. False Question 2 A 95% confidence interval around a RR or OR provides information about the value of the true population parameter (what the value of the true RR or OR is in the underlying source population). Question 3 Match the statement to the correct response. Put the letter corresponding to the response you think best matches the statement.

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1. The investigator rejects the null hypothesis, and the null hypothesis is true. A 2. The investigator rejects the null hypothesis, and the null hypothesis is false. C 3. The investigator fails to reject the null hypothesis and the null hypothesis is true. C 4. The investigator fails to reject the null hypothesis and the null hypothesis is false. B Question 4 Insomnia in young women and subsequent depression The University of South Florida Sleep Study, a long-term prospective study, was used to study the relation between self-reported sleep disturbances and subsequent clinical depression and psychiatric distress. A total of 1,500 women provided information on sleep habits during graduate school at the College of Public Health at University of South Florida (classes 1973-1985) and have been followed since graduation. During a median follow-up time of 15 years (range 3-22), 112 women developed clinical depression (cumulative incidence at 40 years of age 12.2%), including 15 suicides. In Cox proportional hazards analysis adjusted for age at graduation, class year, parental history of clinical depression, coffee drinking, and measures of temperament, the relative risk for clinical depression was greater in those who reported insomnia in graduate school (relative risk (RR) 2.3, 95% confidence interval (95% CI) 1.3 - 3.5) compared with those who did not and greater in those with difficulty sleeping under stress in graduate school (RR 1.9, 95% CI 1.2-2.9) compared to those who did not report difficulty. There were weaker associations for those who reported poor quality of sleep (RR 1.7, 95% CI 0.7 - 3.3) and sleep duration of 6 hours or less (RR 1.6, 95% CI 0.9 - 2.5) with development of clinical depression. Similar associations were observed between reports of sleep disturbances in graduate school and psychiatric distress assessed in 1998 by the General Health Questionnaire. These findings suggest that insomnia in young women is indicative of a greater risk for subsequent clinical depression and psychiatric distress that persists for at least 12 years. Evaluate the following statements as either correct or incorrect using information from the abstract. Question 4a The true population parameter describing the association between sleep duration of 6 hours or less (RR=1.6) and the development of clinical depression could be 1.0.
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