Translations:Advanced Field Epi:Manual 1 - Disease Investigation/330/en
For example, if you are looking for evidence of previous exposure to a chemical that is suspected as a causal factor for a disease in fish, farms with and without the disease may be investigated regarding chemical use. In such a case, all farms should be questioned with equal vigour, and with equal adherence to non-leading questions to avoid triggering "recall bias" as much as possible.