A birthday party was attented by 200 people out of which 55 people develops food poisoning. what is the attack rate
**Core Concept**
The attack rate is a measure of the proportion of individuals exposed to a pathogen who develop the disease. In epidemiology, it is calculated as the number of cases divided by the number of exposed individuals, multiplied by 100 to express it as a percentage.
**Why the Correct Answer is Right**
To calculate the attack rate, we need to divide the number of people who developed food poisoning (55) by the total number of people who attended the party (200), and then multiply by 100. This will give us the percentage of people who were exposed to the pathogen and developed the disease.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely to be incorrect because it does not provide a calculation. The attack rate cannot be determined without dividing the number of cases by the number of exposed individuals.
**Option B:** This option is incorrect because it does not take into account the number of exposed individuals. The attack rate needs to be calculated by dividing the number of cases by the number of exposed individuals.
**Option C:** This option is incorrect because it does not provide a calculation. The attack rate cannot be determined without dividing the number of cases by the number of exposed individuals and then multiplying by 100.
**Option D:** This option is likely to be incorrect because it does not provide a calculation. The attack rate cannot be determined without dividing the number of cases by the number of exposed individuals and then multiplying by 100.
**Clinical Pearl / High-Yield Fact**
The attack rate is an important measure in epidemiology as it helps to determine the severity of an outbreak and the effectiveness of public health interventions.
**Correct Answer:** 27.5. 27.5%