Following is true about attack rate EXCEPT: (A) It is a type of prevalence rate, (B) Expressed as percentage, (C) Reflects extent of epidemic, (D) Total population at risk is taken as denominator
Answer is A. 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