Home › SMLE (Saudi Medical Licensing) › Epidemiology and Biostatistics › Measures of Risk › At a corporate picnic, 99 people ate potato sala…
At a corporate picnic, 99 people ate potato salad and 30 of them developed gastroenteritis. What is the food-specific attack rate?
A23.3%
B30.3%
C3.3%
D69.7%
Answer & Solution
Correct answer: B. 30.3%
1. A food-specific attack rate divides the people who ate a food and fell ill by everyone who ate that food.
2. 30 divided by 99 equals 0.303.
3. Multiplying by 100 gives 30.3%.
4. 69.7% is the complement, the share of potato salad eaters who stayed well.
5. 23.3% comes from dividing 30 by 129, which double counts the ill, and 3.3% comes from inverting the fraction and slipping the decimal point.
_Source: CDC Principles of Epidemiology in Public Health Practice (3rd ed., US federal, public domain), Lesson 3 "Measures of Risk", section Definition of incidence proportion_
Related questions
Among wedding guests, 50 of the 53 who ate cake became ill. What does the fraction 50 overVaricella struck 11.8% of vaccinated children and 42.9% of unvaccinated children. What is What distinguishes vaccine efficacy from vaccine effectiveness?At a wedding, 50 of 53 cake eaters and 4 of 26 non-eaters fell ill. What share of illness Lung cancer mortality was 0.57 per 1,000 per year among light smokers and 0.07 among nonsmInfirmary visits for acute respiratory illness ran at 11.6 per 1,000 tourists per week in Why is the odds ratio the measure of choice in a case-control study?In a case-control study, 32 of 40 case-patients and 20 of 80 controls had stored maize ind