The prevalence of previously 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 sugar content. A value of 180 mg percent or higher is considered positive. The sensitivity and the specificity associated with this screening are 22.9% and 99.8% respectively.
a. Set up a two by two table with the appropriate numbers in each cell of the table. Round to the nearest whole number, but only after you have completed all the calculations down through and including item f). (1 pt. per box including totals)
+ - Total
Total
Prevalence = 1.5%
Population = 10,000
Sensitivity = 22.9%
Specificity = 99.8%
Calculate the following values: (2 pts. each)
b. The percentage of false positives among all those without disease (the type I error rate).
c. The percentage of false negatives among all those with disease (the type II error rate).
d. The predictive value of a positive test.
e. The predictive value of a negative test.
f. Based on the calculations above, how many false positives and negatives will occur if 100,000 people are screened?