To calculate the average of a group of numbers, first add the numbers together and then divide by the amount of numbers that are in the group. The formula for average is: sum/(quantity of numbers.)
The average is also called an arithmetic mean. It is used to describe the best estimate of a single number for a group of numbers. Other terms used to describe groups of numbers are median and mode. The mode is the number that shows up frequently in the sample while the median is the middle number if the sample was arranged in numerical order.