<prompt> Calculate the specificity of the screening test:rn rn rnrnrnrnScreening test resultsrnrnrnDiseasedrnrnNot diseasedrnTotalrnrnrnrnPositivernrnrn400rnrnrn200rnrnrn600rnrnrnrnrnNegativernrnrn100rnrnrn600rnrnrn700rnrnrnrnrnTotalrnrnrn500rnrnrn800rnrnrn1300rnrnrnrn70 per cent75 per cent80 per cent85 per cent  <response>: Specificity is the ability of a test to identify correctly those who do not have the disease, that is, the percentage of true negatives among those not diseased. In the above question, there are 600 true negatives among 800 who are not diseased. Hence, the specificity is 600800x100 75 per cent. Ref: Parks Textbook Of Preventive And Social Medicine, By K. Park, 19th Edition, Pages 118, 119. 