<prompt> Denominator of positive predictive valueNumber of true negatives number of false negativesNumber of true positives number of true negativesNumber of true positives number of false positivesNumber of true positives number of false negatives  <response>: Ans. c Number of true positives number of false positives Ref. Park PSM 22ndpg. 131.TopicEquation SensitivitySensitivity a--acSpecificitySpecificity d-bdPositive predictive valuePPV a--a b Negative predictive valueNPV d--cd Relative riskRR a--a b c--cd Attribute riskAR a--abc--cdHardy-Weinberg equilibriumP2 2pq q2 1p q lThe positive predictive value. or precision rate, is the proportion of patients with positive test results who are correctly diagnosed. It is considered the physicians gold standard, as it reflects the probability that a positive test reflects the underlying condition being tested for.Related calculationsFalse positive rate a FPFP TN 1818182 90 1 - specificityFalse negative rate b FNTPFN 1 21 33 1 - sensitivityPower 1 - bDefinition:PPV Number of True Positives---Number of true positives Number of False Positives or, alternatively.PPV Sensitivity prevalence---Sensitivity prevalence 1 - specificity 1 - prevalenceThe negative predictive value is the proportion of patients with negative test results who are correctly diagnosed.NPV Number of True Negatives---Number of True Negatives Number of False Negatives or alternatively.NPV Specificity x 1 - prevalence---Specificity x 1 - prevalence 1 - sensitivity x prevalence 