<prompt> In a village having population of 1000, we found patients with ceain disease. The results of a new diagnostic test on that disease are also follows: Test Result: Disease Present Present 180 400 - 20 400 What is the percent prevalence of disease?0.221820  <response>: Village population 1000 Total disease person 18020 200 In this 180 true positive so 20200-180 false negative by test. But we want only percentage prevalence of disease only. Prevalence 2001000 x 100 20 Prevalence of disease is 20 in village prevalence of disease by using diagnostic test used 1801000 x 100 18 Ref: Parks Textbook Of Preventive And Social Medicine By K. Park, 17th Edition, Page 56; Parks Textbook Of Preventive And Social Medicine By K. Park, 18th Edition, Page 55 