20. The key feature of an analytic (epidemiologic) study is: (Select only one answer)
A. Analysis by time, place, and person
B. Calculation of a risk ratio or odds ratio
C. Use of Epi Info to analyze the data
D. Presence of a comparison group
21. Disease control measures can be directed at the:
A. Agent
B. Source
C. Mode of transmission
D. Portal of entry
E. Host susceptibility
Use the information in the following paragraph and data in the table for Questions 22–25.
An outbreak of gastrointestinal disease occurred 24-36 hours after people had attended a wedding. Of the 203 attendees (including the bride and groom), 200 completed questionnaires, and 50 reported illness compatible with the case definition. Tabulated food consumption histories are presented in the table below.