Statistical Measures

Outbreak Practice Exercises

Answer questions a through f by analyzing the data in Table 8, Table 9 and Table 10.

1. Grouping the dates of onset into 7-day intervals, create a frequency distribution of number of cases by week and city or non-city residence.
2. Use the line listing in Table 8 and the ward population data in Table 9 to compute area-specific attack rates for the city wards. Which ward of the city has the most cases? Which ward has the highest attack rate?
3. Calculate the ratio of female-to-male cases.
4. Calculate the proportion of cases that are female.
5. Use the line listing and the age- and sex-specific population data in Table 10 to compute age- and sex-specific attack rates. Which age/sex groups were at greatest risk? Which age/sex groups were at lowest risk? (Hint: Table 10 is limited to city residents. Whom should you include in the numerator of your attack rates?)
6. Calculate the relative risk for persons age 40 to 59 years versus persons age 20 to 39 years.

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