A definition of population for a study consists of:
- A description of the observations.
- A description of which observations are and are not included.
In political polling, government and social research, the distinction between the observations and the rules regarding which observations are and are not included is often trivial (e.g., where the unit is people that are eligible to vote in a forthcoming presidential election). However, in many other disciplines the distinction is more useful. For example:
- A study of cat food buyers may define the observation as people that buy cat food but the description of the observations which are and are not included can be substantially more refined, such as: people that have purchased catfood in California during the past 3 months from a supermarket.
- A study looking at attitudes towards chewing gum may include people that do not chew chewing gum based on various criteria of whether or not they may potentially chew chewing gum (see Market Definition).
Also known as
- The universe
- B. S. Everitt (2002): The Cambridge Dictionary of Statistics, Second Edition, Cambridge