<prompt> A malarial survey is conducted in 50 villages having a population of one lakh. Out of 20000 slides examined, 500 turned out to be malaria positive. The annual parasite incidence is -2050.500.40  <response>: -Annual parasite incidence. confirmed cases during one year 1000 --- Population under surveillance 0.5 -It is based on intensive active and passive surveillance and cases are confirmed by blood examination. Reference : Parks textbook of preventive and social medicine, 23rd edition, pg no:261 