Parameters and Statistics

A parameter is a numerical quantity that describes some characteristic of a population. Parameters are often estimated since their value is generally unknown, especially when the population is large enough that it is impossible or impractical to obtain measurements for all observations. Parameters are normally represented by Greek letters. The most common parameters are the population mean and variance, represented by the Greek letters m and s² , respectively.

A statistic is a quantitative value that is calculated from the observations in a sample. They are usually represented by lowercase English letters with other symbols. The sample mean and variance, two of the most common statistics derived from samples, are denoted by the symbols x and s², respectively.