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This assignment is based on the learning objectives and concepts in Topic 1. There are a total of 46 marks and this assignment will contribute 20% towards the total assessment for this subject.
Your assignment should be typed, with adequate space left between questions. Assignments should be submitted via vUWS with cover sheet (see specific instructions relating to Assignment submission Learning guide on vUWS).

Be as brief as possible in your answers, and use the number of marks for a question as a guide to how much to write. No answers need to be longer than a few short sentences or short paragraphs.

Remember to save your assignment as:

Remember to submit your final version in the final Turnitin link. Leave the questions in the body of text as is (with the quotation mark it will not be included as similarities).

Q1. “In a health survey in a city neighbourhood 431 people aged 65 or above were examined, 52 were found to have congestive heart failure. Each person was examined once, but the examination was staggered over a period of two years (given the sample was relatively big n=431)”
a.    “What was the prevalence of congenital heart failure?”  [ Mark 2]

b.     “Is it a point or period prevalence?”  [ Mark 2]

Q2.  “This table presents the incidence rate IR (cumulative) and population size for two regions”
Region A    Region B
Population  size    10,000    5000
IR of gastroenteritis     10 per 100    5 per 100

“Which of the following statements are True (if Any) – explain your answer by calculation if needed”
a.    There were the same number of cases in both regions      [mark 1]

b.    There were twice as many cases in region A then region B  [mark 1]

c.    The risk of incurring the disease during the year was about the same for individual in region A as for those in region B [mark 1]

d.    The risk of incurring the disease during the year was twice as high for individuals in region A as for those in region B.  [mark 1]
Q3 – “What will be the incidence rate of region A and Region B combined? [mark 4]

Q4. “In an army base, where there is a complete change of personnel every 3 months and the total base is always 1000 (i.e., every 3 months 1000 new soldiers arrive and 1000 leave). It was found that 2000 soldiers incurred syphilis every year. What is the yearly cumulative incidence of syphilis in this base? “  [mark 2]

Q5. “Now assume that in each three-monthly batch of 1000 soldier there were 250 soldiers who contracted syphilis after exactly one month (let’s say on the payday) and another 250 who did so after precisely two months”.
a.    Calculate the sum total of the soldiers’ period of exposure to risk (person-time) for use as denominator [mark 2]

b.    Calculate the person-time incidence rate [mark 2]

Q6. “The following table depicts the age distribution and the number of HIV/AIDs cases that exist in each age group”
Intravenous drug (IVD) users    Homosexual (men to men sex)
Age group (years)    Population size    # HIV/AIDs cases    Population size    # HIV/AIDs cases
18-30    55    4    112    30
31-55    8    1    141    32
56+    2    0    95    15

a.    “Compare the crude prevalence of HIV/AIDS between the two groups? (Show the process of calculation not just one final number)”  [mark 2]

b.     “Compare the age-specific prevalence between the groups, is there any pattern?”  [mark 2]

c.     “Would it be correct to compare the crude prevalence between the two group?  Explain why yes or why not  (no more than 60 words)”    [mark 2]
d.     “Compute the direct standardised prevalence of HIV/AIDs for intravenous drug users using the age distribution of homosexuals. Express your results in percent”.  [4 marks]

e.    Summarise the differences between the crude prevalence and the age-standardised rate. (no more than 100 words) 2 marks

Q7.  “A random sample of middle-age sedentary overweight males was selected from four census tracts in four countries, and each man was examined for coronary artery disease. All those having the disease were excluded from the study. All other were randomly assigned to Mediterranean diet group, which followed a 2-year program of this diet, or to a control group, which received educational materials about healthy lifestyle. Both groups were observed half-yearly for any difference in incidence of coronary artery disease”.

a)    Study type/design [2 marks]:

b)    Key feature(s) what led your decision of the study design from this text: [2 marks]

Q8.  “The hypothesis that meat consumption can increase the risk of colon cancer was investigated in 22 countries.  Investigators checked the sales per-capita of meat (e.g., beef, lamb, pork and chicken) and then looked at the number of colon cancer death per 100,000 in each country. They found high correlation (r=0.82) between mortality from colon cancer and consumption of meat; the higher the consumption of meat per capita in the country the higher the death rate from colon cancer”

a)    Study type/design [2 marks]:

b)    Key feature(s) what led your decision of the study design from this text: [2 marks]

Q9.  Read the following abstract and answer the following questions
Background: Although gait speed slows with age, the rate of slowing varies greatly. To date, little is known about the trajectories of gait speed, their correlates, and their risk for mortality in older adults.
Methods: Gait speed during a 20-m walk was measured for a period of 8 years in initially well-functioning men and women aged 70–79 years participating in the Health, Aging and Body Composition study. We described the trajectories of gait speed and examined their correlates using a group-based mixture model. Also risk associated with different gait speed trajectories on all-cause mortality was estimated using a Cox-proportional hazard model.
Results: Of 2,364 participants (mean age, 73.5±2.9 years; 52% women), we identified three gait speed trajectories: slow (n = 637), moderate (n = 1,209), and fast decline (n = 518). Those with fast decline slowed 0.030 m/s per year or 2.4% per year from baseline to the last follow-up visit. Women, blacks, and participants who were obese, had limited knee extensor strength, and had low physical activity were more likely to have fast decline than their counterparts. Participants with fast decline in gait speed had a 90% greater risk of mortality than those with slow decline.
Conclusion: Despite being well-functioning at baseline, a quarter of older adults experienced fast decline in gait speed, which was associated with an increased risk of mortality.

a)    What is the research question/s [2 marks]

b)    What is the exposure   [2 marks]

c)    What is the outcome   [2 marks]

d)    What is the study design – what led your decision of the study design from this text        [2 marks]