EPI420 Midterm Review, Spring 2008
1. What is the crude prevalence of MS among people of different ethnicities in Seattle and
1.42 MS cases per 1000 people
1.59 MS cases per 1000 people
2. What is the exposure, outcome, and confounder?
3. Why does the crude prevalence differ if the prevalences of MS within racial groups in the
two cities are the same?
The prevalence of MS is higher in white race groups and there are
proportionately more white people in Seattle (399,000/570,000)*100=70.0%
than San Diego (763,000/1,267,000)*100=60.2%.
4. Use a standard population by combining the populations of San Diego and Seattle and
calculate the adjusted prevalence for each city.
Race Specific Rates
2 cases per 1000 people