An artificial number that we create to represent a set of numbers.The arithmetic mean or average (called mean) of a_{1}, a_{2}, a_{3}, . . ., a_{n} is given by:

(a_{1}+a_{2}+a_{3}+. . .+a_{n})/n

If the set of numbers a_{1}, a_{2}, a_{3}, . . ., a_{n} occur with frequencies f_{1}, f_{2}, f_{3}, . . ., f_{n}, then the arithmetic mean is given by:

(f_{1}a_{1}+f_{2}a_{2}+f_{3}a_{3}+ ... +f_{n}a_{n})/(f_{1}+f_{2}+f_{3}+ ... +f_{n})

The geometric mean of a_{1}, a_{2}, a_{3}, . . ., a_{n} is given by:

(a_{1}×a_{2}×a_{3}×...×a_{3})^{1/n}