A parameter is a numerical quantity measuring some aspect of a population of scores. For example, the mean is a measure of central tendency.

Greek letters are used to designate parameters. At the bottom of this page are shown several parameters of great importance in statistical analyses and the Greek symbol that represents each one. Parameters are rarely known and are usually estimated by statistics computed in samples. To the right of each Greek symbol is the symbol for the associated statistic used to estimate it from a sample.

Quantity Parameter Statistic
Mean μ M
Standard deviation σ s
Proportion π p
Correlation ρ r