The "eligible population" depends on the purpose and design of the specific dataset. If the dataset is population-based and aims to cover the entire population of a given territory, the "eligible population" is the population of that entire territory. If it is a specific registry, for example, a tumor registry, the "eligible population" will be the entire population diagnosed with a tumor in the relevant geographic area. Population coverage must be calculated based on this "eligible population." If the dataset is designed as a random sample, the "eligible population" will be the population from which the sampling is performed.