Modél statistik: Béda antarrépisi

# 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.