Translations:Advanced Field Epi:Manual 1 - Disease Investigation/371/en

From the above results, and with reference the above table, Organism 2 is the only one which is statistically associated with an animal being a case, despite Organism 3 being isolated more frequently from cases. The reason for this conclusion is that the sample size of 30 is insufficient to detect a statistical difference in the isolation rates from cases and non-cases for Organisms 1 and 3, but is sufficient for Organism 2. This does not 'prove' that Organism 2 is the primary pathogen (as it could be an opportunistic, secondary invader), but by examining a reasonable number (in this case, 30) of cases and non-cases we are much better able understand the relative importance of the three organisms.