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Community A has the higher crude mortality rate but the lower age-adjusted rate. What does that indicate?
ACommunity A's population is on average the older one
BCommunity B's population is on average the older one
CThe two communities share an identical age structure
DA calculation error was made somewhere in the figures
Answer & Solution
Correct answer: A. Community A's population is on average the older one
1. A crude mortality rate carries both the real death experience and the age structure of the population.
2. Age adjustment strips out the age structure, leaving only the death experience.
3. Community A's rate falls once age is removed, so age was inflating its crude figure.
4. Age inflates a crude rate when the population is old, so Community A is the older one.
5. Identical age structures would leave the crude ranking unchanged after adjustment, so the third option cannot hold.
6. This reversal is the expected behaviour of the two measures, not a sign of arithmetic error.
_Source: CDC Principles of Epidemiology in Public Health Practice (3rd ed., US federal, public domain), Lesson 3 "Measures of Risk", section Age-adjusted mortality rates_
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