Question

2. Sometimes we use the phrase “looking for a needle in the haystack” to refer to the difficulty of locating one object in the midst of a lot of others. Explain how this phrase is relevant to the connection between prevalence of a disease and the usefulness of testing the general population.

Answer 1

Let there be a number of diseases in the general population, We are interested in studying the prevalence of a particular disease in the general population that is not affected by any other diseases. The spread of the diseased people, those with only a particular disease of our study. We need to falsify the presence of any other diseases through testing. Really if we need to study those affected with only with one particular disease who represents the target general populations is similar to "looking for a needle in the haystack".