# Calculating-and-Interpreting-Measures-of-Occurrence-and-Association

Week 2 Assignment: Measures of Occurrence and Association

NOTE: For this assignment it is important that you show your work. Problems where work is not shown will not receive full credit, even if the answer is correct. Please see the Week 2 Assignment Rubric for more details about the grading criteria for this assignment.

Incidence Density

A cohort study (hypothetical) was conducted to look at survival after experiencing a myocardial infarction (heart attack). Ten participants were followed for 3 years, resulting in the following table:

 Follow-up Time (Months) Event 3 Death 5 Censored 8 Death 12 Death 17 Censored 19 Censored 27 Death 32 Censored 36 Followed until end of study period 36 Followed until end of study period
• What is the cumulative survival probability at the end of the follow-up period?
• Using the same data, calculate the overall death rate per 100 person-years.
• Calculate the rates separately for each of the 3 years of follow-up.
• Given the information above, is it appropriate to report an overall 3-year death rate for this study? Why or why not?

Attributable Risk

A hypothetical cohort study looked at the association between family history and the risk of developing Alzheimerâ€™s disease. The results were as follows:

 Alzheimerâ€™s Disease No Alzheimerâ€™s Disease Totals Incidence of AD Family History 50 1,950 2,000 25 per 1,000 No Family History 25 2,975 3,000 8.3 per 1,000
• Calculate the attributable risk for Alzheimerâ€™s disease due to family history. Interpret the calculation in words.
• Assume the prevalence of family history in the general population is 5%. Calculate the population attributable risk and interpret it in words.
• Now assume the prevalence of family history in the general population is 25%. What effect does this change have on the estimate of the population attributable risk? Discuss the relationship between the population prevalence of exposure and the population attributable risk. Why is it important to understand this relationship as a public health professional?