Definition
Arithmetic mean
The arithmetic mean is the sum of numerical values divided by the number of values.
What it means
Imagine pouring all the amounts into one pool, then sharing the total equally among the data places. The equal share is the arithmetic mean. Because every value contributes to the total, one very large or small value can move the mean.
Remember it
Pool every value, then give each data place an equal share.
Example
Four plant heights are 12 cm, 15 cm, 15 cm, and 18 cm. Their total is 60 cm, and 60 ÷ 4 = 15 cm, so the arithmetic mean height is 15 cm.
Watch for
The arithmetic mean is for numerical values. A category label such as red or bus cannot be added and divided.
Common mix-up
The median is the middle value after ordering; the arithmetic mean uses the sum of every value.
Exact meaning
For a finite list of numerical values, the arithmetic mean is the sum of the values divided by the number of values.