Adding all the observations and dividing the sum by the number of observations results the arithmetic mean. Suppose we have the following observations:

10, 15,30, 7, 42, 79 and 83

These are seven observations. Symbolically, the arithmetic mean, also called simply

*mean *is

*x *= å*x/n, *where *x *is simple mean.

= 10 + 15 + 30 + 7 + 42 + 79 + 83/ 7

= 266/7= 38

It may be noted that the Greek letter m is used to denote the mean of the population and *n *to denote the total number of observations in a population. Thus the population mean m = å*x/n. *The formula given above is the basic formula that forms the definition of arithmetic mean and is used in case of ungrouped data where weights are not involved.