1 in 4 of adult sea lions that where necropsied after dying (by disease or accident). The title leads to conclude that the 25% of the population has the disease

1 in 4 of adult sea lions that where necropsied after dying (by disease or accident). The title leads to conclude that the 25% of the population has the disease, but this wouldn't be supported by the data, because is not a random sample. This is a sample rich in the "ill seals" subconjunct, and therefore not necessarily representative of the whole population. Is a common problem when we study stranded cetaceans or seals. Linking herpesvirus with the cancer is the more interesting part.