In statistics, a population is the complete set of items for the subject to be analysed.

For instance, when analysing a particular group of people, the population would include every single person who fit into that group.

A population parameter is a number describing the population. An example of this is the mean height for a class of 50 VCE students. In order to calculate the population mean, it would involve recording the heights of every student in the class. When working with population means, the symbol $\mu$ (mu) is used. Since all members of the population are included, it should be noted that population parameters are therefore fixed values for that specific population.

Typically, populations are large and collecting data would be either impractical or impossible. Because of this, samples are used to represent a population.

The notation for standard deviation between the population and the sample data also change.