# Population A population is a group of interest in its entirety. We usually want to study a population, but due to real-world constraints, it is presumed to be impossible to collect data from *everyone* in this group. >[!example] >For a clinical trial studying a new oncodrug for advanced breast cancer, a relevant population might be all women aged 55 and older. Researchers will create inclusion and exclusion criteria to refine and clarify the precise population they wish the study. For example, a study looking at asthma might have exclusion criteria to exclude people with preexisting lung conditions like bronchitis. Because we cannot observe a population in its entirety, we typically collect data on a small subset of the population called a [[Sample|sample]]. --- # References [[Fundamentals of Biostatistics#Chapter 6 - Estimation]]