This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Denominator in sensitivity is ? 
Select and explain. 
A. Total number of healthy people, B. Total number of diseased people, C. Total number of people showing positive results, D. Total number of people showing negative results
B: Total number of diseased people
Answer: B: Total number of diseased people 
Explanation: Ans. is 'b' i.e., Total number of diseased people i) SensitivityIt is the percentage of diseased people that who are diagnosed as having disease.Total number of diseased people = True positive + False negative.Number of people (among diseased people) diagnosed as having disease = True positives. ii) SpecificityIt is the percentage of healthy people who are identified as healthy.Total number of healthy people = True negatives + False positivesNumber of healthy people who are identified as healthy = True negatives