Mean
There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set. For a data set, the arithmetic mean, also known as "arithmetic average", is a measure of central tendency of a finite set of numbers: specifically, the sum of the values divided by the number of values. The arithmetic mean of a set of numbers x1, x2, ..., xn is typically denoted using an overhead bar, . If the data set were based on a series of observations obtained by sampling from a statistical population, the arithmetic mean is the sample mean to distinguish it from the mean, or expected value, of the underlying distribution, the population mean (denoted or ). Outside probability and statistics, a wide range of other notions of mean are often used in geometry and mathematical analysis; examples are given below. (Wikipedia).
