Population A population consists of an entire set of objects, observations, or scores that have something in common. For example, a population might be defined as all males between the ages of 15 and 18.
Some populations are only hypothetical.
Consider an experimenter interested in the possible effectiveness of a new method of teaching reading. He or she might define a population as the reading achievement scores that would result if all six year olds in the US were taught with this new method. The distribution of a population can be described by several parameters such as the mean and standard deviation. Estimates of these parameters taken from a sample are called statistics.