This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Statistical Tests, Subject name: Social & Preventive Medicine
On a screening test, negative result is seen in 50% of non- diseased population and positive result in 10% healthy population. Calculate specificity: 
Select and explain. 
A. 0.5, B. 0.6, C. 0.83, D. 0.9
C: 0.83
Answer: C: 0.83 
Explanation: Ans. (c) 0.83Ref: K. Park 21sted. /113* The screening test shows true negative result in 50% of diseased population* In 10% healthy population, the test shows positive result. That means 10% false positive.Putting this into formula:True Negative--------------------------False positive + True Negativex 100 50------10 + 50x 100 50------60x 100 = 83% = 0.83