ABSTRACT
Often it is necessary to decide whether a characteristic exists in a subject or item based on some screening test. We shall consider that the test is binary in that it indicates T (or positive) for the presence of the characteristic, T ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203742310/579ac1f2-f40a-4dc7-b13d-cf4179828552/content/eq948.tif"/> (or negative) for its absence. The merit of the test will depend on its accuracy in determining whether or not the characteristic exists in items or individuals to whom the test is administered that either possess the characteristic or do not.
