A statistical model is used in applied statistics. Three basic notions are sufficient to describe all statistical models.
We choose a statistical unit which we will observe directly. Multiple observations of the same unit over time is called longitudinal research[?]. Observations of a variety of statistical attributes[?] is a common way of studying relationships among the attributes of a single unit.
We may really be interested in a statistical population (or set) of similar units rather than in any statistical unit per se. Survey sampling offers an example of this type of application.
... census of 2000, there are 14,078 people, 4,578 households, and 3,731 families residing in the town. The population density is 1,322.5/km² (3,428.5/mi²). There ...