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Outbreak Practice Exercises

Answers:

a. 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.

Week of Onset
Week
City
Non-City
Total
Total
 

b. 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 (round answers to one decimal place)?

Area-Specific Attack Rates
Ward #
# Cases
Population
Rate per 1,000
Unk City
 
 
Total City
County
Out of County
 
 
Total
 
 
 

c. Calculate the ratio of female-to-male cases (round answer to one decimal place).

d. Calculate the proportion of cases that are female (round answer to one decimal place).

e. 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 (round answers to one decimal place)? (Hint: Table 10 is limited to city residents. Whom should you include in the numerator of your attack rates?)

City Cases
Age group
Male
Female
Total
-
-
-
-
≥
Total
 
Age- and Sex-Specific Attack Rates per 1,000 Population
Age group
Male
Female
Total
0 - 9
10 - 19
20 - 39
40 - 59
≥ 60
Total
 

f. Calculate the relative risk for persons age 40 to 59 years versus persons age 20 to 39 years (round answer to one decimal place).