Question 1: In 1970 the crude mortality rate (all causes) for Guyana (a developing country) was 6.8 per 1,000 and for the US it was 9.4 per 1,000. Can the lower crude mortality rate in Guyana be explained by the fact that the US has a larger population? [2 marks] No more the 50 words Question 2: In 2012, a group of 4,233 men and women aged 20 years were recruited from the general population and assessed for HIV virus. 288 participants were found to have HIV when tested at baseline. Participants who did not test positive for HIV in 2012 were followed-up and assessed again after 4 years of follow-up (only those who previously had tested negative for HIV were tested again at follow-up). A further 99 cases of HIV were identified during this 4 year period, either diagnosed during the interim or diagnosed during the study assessment. (It is assumed that once participants contract HIV they remain HIV positive without recovery (a) What was the prevalence of HIV among study participants in 2012? [2 Marks] (b) What was the prevalence of HIV among study participants after 4 years of follow-up? Assume no loss to follow-up. [2 marks] (c) What was the cumulative incidence of HIV among study participants over the study period? [4 marks] (d) Calculate the total number of person-years at risk during the 4 year period. (Assume that HIV was acquired randomly during the 4 year period. That is, those who acquired HIV were at risk for half the time of those who did not acquire HIV. [4 marks] (e) What was the incident rate of HIV among participants for the 4 years. [4 marks] (f) Assuming that the incidence rate of HIV remains constant, what should happen to the prevalence of HIV in this cohort over time?[2 mark] Question 3: Question 2 relates to the following table of male suicide in the Sydney metropolitan area, stratified by quintile of socio-economic status (SES). (Only the lowest and highest SES groups are shown). Note: 5 years of death data are presented. Population data comes from a single census year (2011). It is conventional to present mortality rates as annual average rates. Lowest SES quintile, Suicides Lowest SES quintile, Population Highest SES quintile, Suicides Highest SES quintile, Population Total suicide (All quintiles) Total population (All quintiles) 2011 2011 2011 2011 2011 2011 Males 15-24 195 123,961 116 140,942 779 667,548 25-34 242 134,303 158 134,595 1,044 693,988 35-44 204 133,242 123 135,819 865 688,839 45-54 147 110,680 92 124,576 594 577,128 55-64 89 83,943 55 75,308 364 381,248 65-74 76 73,509 42 56,097 283 304,226 75+ 56 39,197 43 36,293 224 172,856 1,009 698,835 629 703,630 4,153 3,485,833 (a) Calculate the crude suicide incidence rate (per 100,000) for the lowest SES quintile and the highest SES quintile for those aged ≥15 years. [4 marks] (b) Calculate the direct age-standardised suicide incidence rate (per 100,000) for the lowest SES quintile using the highest SES quintile as the standard. [4 marks] (c) Is age an important factor in understanding differences in suicide between low and high SES groups? Using the age-specific data provided, make a specific comment about the difference between the crude suicide rate and the direct age-standardised suicide rate. [4 marks] . (d) Calculate the crude mortality ratio (%) for lowest SES quintile relative to the highest SES quintile [2 marks] (e) What is the directly age-standardised mortality ratio (%) for the lowest SES quintile relative to the highest SES quintile? [2 marks] (f) Using the suicide incidence rates in the highest SES quintile as the standard, what is the indirect age-standardized mortality ratio (%) of the lowest SES quintile relative to the highest SES quintile? [4 marks] Question 4: Discuss advantages and shortcomings of case controls study. (Limit of half a page. Please note: No more than half a page of text will be marked) [4 marks] Question 5: The hypothesis that omega 3 consumption can protect from cardiovascular disease was investigated in 22 countries. Investigators checked the sales per-capita of products containing omega 3 (e.g., fish) and then looked at the number of CVD death per 100,000 in each countries. The found high correlation (r=0.82) between mortality from CVD and consumption of omega 3. [2 mark] a. What is the study type and justify your argument (no more than 50 words) b. Suggest a different study type to test the same hypothesis and explain what you need to do [2 mark] (no more than 100 words)