Mean, Median, Mode

Arithmetic Mean:

• All the values are included in computing the mean.
• The mean is affected by unusually large or small data values.
• The arithmetic mean is the only measure of central tendency where the sum of the deviations of each value from the mean is always zero.

Weighted Mean:

a set of numbers, with corresponding weights is computed from the following formula.

Median:

The midpoint of the values after they have been ordered from the smallest to the largest or the largest to the smallest. There are as many values above the median as below in the data  array.

Note: For an even set of numbers, the median will be the arithmetic mean of the two middle numbers.

• There is a unique median for each data set.
• It is not affected by extremely large or small values and is therefore a valuable measure of central tendency when such values occur.

Mode:

The value of the observation that appears most frewuently.

Geometric Mean:

A set of n numbers is defined as the nth root of the product of the n numbers.

It is used to average percent, indexes and relatives.
Another use of the geometric mean is to determine the average percent increase in sales, production or other business or economic series from one time period to another.
The formula for this type of  problem is