Define prevalence (max 100 words)

Assessment Item 1


Task and Assessment Criteria:

  1. Incidence and prevalence
  2. Define prevalence (max 100 words) 2 marks
  3. Define incidence (max 100 words) 2 marks
  4. Provide the formula that shows the relationship between prevalence and incidence. Explain your answer (max 150 words) 3 marks
  5. Provide one example of an illness or condition that has a high incidence and low prevalence. Explain your answer (max 150 words) 3 marks
  6. Provide one example of an illness or condition that has a low incidence and high prevalence. Explain your answer (max 150 words) 3 marks


  1. Incidence and prevalence

The following table shows the results of a cohort study where 10 people were followed up over a five-year period. During that time, several people stayed healthy for the entire period, some developed disease, some died and some were lost to follow-up.

  1. Calculate the point prevalence of disease in this study at the end of the 4th Express your answer as cases per 100 persons 2 marks
  2. Calculate the person-time incidence rate (incidence density rate) of disease in this study during the entire study period. Express your answer as cases per 100 person-years 2 marks


Person IDStudyLegend
Year 1Year 2Year 3Year 4Year 5Healthy period
1Disease period
2Lost to follow up


  1. Epidemiological sources

This question firstly requires you to identify websites containing data on the issues shown in the table below and record specific information on each issue.

  1. Paste the URL as a link for the Australian data source for EACH issue listed in the table below and provide a summary statistic (count or cost) for Australia and the Northern Territory (NT) 7 marks


Census population count2016  
PES population estimate2016  
Preliminary ERP30 June 2016  
Traffic Accident Deaths 2016  
Lung cancer incidence 2014  
PBS Total Cost of highly specialised drugs (PBS)2016–2017 Total  
MBS Total number of Medicare services (All services = In and Out of Hospital)2016-2017  


The second part of this question you are required to perform calculations based on data located in the cancer, PBS and MBS web sites identified in Q3a.

  1. What were the age-standardised rates (ASR) of lung cancer in the NT and Australia in 2004 and 2014? Comment on the trends in lung cancer rates in the NT and Australia over this decade (max 100 words) 3 marks
  2. What was the cost of HIV/AIDS Antiretroviral Agents in the NT and Australia in 2015-2016 and 2016-2017? 2 marks
  3. How much higher was the 2016-2017 cost of HIV/AIDS Antiretroviral Agents compared with 2015-2016 in the NT and in Australia. Express your answer as a percentage increase 2 marks
  4. How many Medicare services (All Services = In and Out of Hospital) were provided in NSW, QLD, NT and the ACT during 2016-2017? 2 marks
  5. How many Medicare services did each person receive (per capita rate) in these jurisdictions? 1 mark
  6. Discuss why the Medicare services per capita rate in the NT differs from other jurisdictions (max 100 words) 2 marks




  1. Age-standardisation
  2. Fill in the table below with the number of cases of all-cancers combined (ICD-10 codes C00–C97, D45, D46, D47.1, D47.3–D47.5) diagnosed in the Australian population during 2014 and the preliminary ERP as at 30 June 2014 in each age group 3 marks
  3. Using these data, calculate the crude and age-standardised rates of all-cancers combined in the Australian population in 2014 3 marks
  4. Explain why the crude rate differs from the age-standardised rate (max 150 words) 3 marks
Five-year age groupCasesPopulationAge-specific rateStandard population (2001 ERP)Expected number of cases
Total   19,413,240 
Crude rate (rate per 100,000 population) 
Age-standardised rate (rate per 100,000 population) 


  1. Contingency table

The following table contains data collected in a hypothetical small community where all 50 residents were screened for diabetes.


Legend M=Male, F=Female, Y=Diabetic, N=Non-diabetic

  1. Using these data, fill in the number of diabetics and non-diabetics in this community in the 2X2 table below according to sex and total numbers 2 marks
  2. Calculate the prevalence of diabetes among males and females in this community? (Show your answer as a percentage) and comment on the difference in diabetes prevalence among men and women (max 100 words) 3 marks
  3. What is the prevalence of diabetes in the general population? (provide year and reference) 1 mark
  4. Name a population group where the prevalence of diabetes is like the prevalence found in this community and comment on why this population group has a different diabetes prevalence to that of the general population (max 150 words) 4 marks


No diabetes



  1. Measures of association

The following contingency table relates to a hypothetical retrospective cohort study where the investigators wanted to know if consuming vitamin D puts people at a lower risk of fracture.  The investigators examined the medical records of 14,000 elderly people for history of fracture and vitamin D consumption during the previous ten years.

  1. Compare the risk of fracture among the people who did not consume vitamin D with the risk among those who did consume Vitamin D. Explain your answer ie what does the relative risk mean in this context? (max 100 words) 3 marks
  2. How much fracture incidence could have been avoided in the non-consumers if they had consumed vitamin D? (Show your answer as a percentage)2 marks
  3. How much fracture incidence could have been avoided in the entire cohort if they had all consumed vitamin D? (Show your answer as a percentage) 2 marks
  4. Thinking about your answer to question 6C do you think it would be good public policy to recommend elderly people include vitamin D based on the findings of this study. Explain your answer? (max 150 words) 3 marks
Supplement statusFractureNo fractureTotal
No vitamin D1505,8506,000
Vitamin D1607,8408,000



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