Central Tendency

Mean

Mean (also known as expectation or average) is defined as the sum of all deviations divided by the total number of observations. Mean is considered as the best measure of central tendency when data is normally distributed.

Some properties of expectation (mean) for a random variable X are:

Median

Median is defined as the middle value in a series of data when arranged in ascending order of importance. The median in a series of ordered (ascending) values is the value at which there are just as many values less than it as there are greater than it. Median is considered as the best measure of central tendency when data is skewed or has outliers.

Mode

The mode is defined as the observation which occurs a maximum number of times. The mode is the number with the highest frequency. The mode is considered as the best measure of central tendency when data is measured on the nominal scale of measurement.