Epidemiology for Public Health Practice 5th Edition by Robert Friis,Thomas Sellers

Exercise 10

The prevalence of undetected diabetes in a population to be screened is approximately 1.5%, and it is assumed that 10,000 persons will be screened. The screening test will measure blood serum glucose content. A value of 180 mg% or higher is considered positive. The sensitivity and specificity associated with this screening test are 22.9% and 99.8%, respectively.
a. What is the predictive value of a positive test?
b. What is the predictive value of a negative test?