<prompt> All are true of attack rate exceptIt is type of prevalence rateExpressed as percentageUsed when population is exposed to risk for a limited period of timeReflects extent of epidemic  <response>: Ref:Parks 23rd edition pg 61 Attack rate case rate is an incidence rate. Usually expressed in percent Used only when population is exposed to risk for a limited period of time as in an epidemic. Reflects the extent of epidemic. Attack rate no. of new cases of a specified disease during a specified time interval Total population at risk during the same interval x100 