Translations:Advanced Field Epi:Manual 2 - Diagnostic Tests/194/en
For example: If 20 animals are selected from a herd or flock with a true prevalence of 0.05 (5%) and are tested using a test with Se=0.9 and Sp=0.99, and all 20 have a negative result, the probability that there are one or more infected animals in the group is about 0.1 (10%). In addition, the probability that all 20 animals will have a negative test result is about 0.33 (33%).