A screening test was positive in 50% of diseased and 10% of healthy population. What is the specificity of the test?: (A) 0.5, (B) 0.9, (C) 0.83, (D) 0.064
Answer is B. Screening Test Gold Standard Positive Negative Positive 50 10 Negative 50 90 Specificity= True Negative / True Negative + False Positives = 90/90 + 10 = 90/100 = 0.9