The mean (arithmetic mean) is the sum of all values divided by the count of values.
The mean, also called the average, is the most common measure of central tendency. It provides a single value representing the typical value in a dataset. However, the mean is sensitive to outliers (extreme values), which can skew it. The weighted mean, geometric mean, and harmonic mean are variations used for specific situations. The mean is used everywhere from calculating grades to analyzing economic data.
The arithmetic mean was used by ancient mathematicians. The Pythagorean school studied means (arithmetic, geometric, harmonic) around 500 BCE. Modern statistical mean analysis developed in the 19th century with the work of Adolphe Quetelet, who applied statistical methods to social sciences, and Francis Galton, who studied correlation and regression.