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What is Following is true about attack rate EXCEPT and explain in detail?
An attack rate is an incidence rate (usually expressed as a percent), used only when the population is exposed to risk for a limited period of time such as during an epidemic. It reflects the extent of an epidemic. Attack rate = Number of new cases of a specified disease during a specified interval / Total population at risk during the same interval x 100 Ref : Park 23rd edition Pgno : 131