Question

The Army Medical Corps is concerned about the intestinal disease X. From previous experience they

know that soldiers suffering from the disease invariably harbor pathogenic organisms in their feces and

that for all practical purposes every disease stool specimen contains these organisms. The organisms are

never abundant, however, and thus only 20% of all slides prepared by the standard procedure contain

some of them. (We assume that if an organism is present on a slide, it will be seen.) How many slides

per stool specimen should the laboratory technicians prepare and examine to ensure that if a specimen

is positive, it will be erroneously diagnosed negative in less than 1% of the cases (on the average)?

Answer 1