Referred to as average deviation, it is defined as the sum of the deviations(ignoring signs) from an average divided by the number of items in a distribution The average can be mean, median or mode. Theoretically median is d best average of choice because sum of deviations from median is minimum, provided signs are ignored. However, practically speaking, arithmetic mean is the most commonly used average for calculating mean deviation and is denoted by the symbol MDMD.

We’re going to discuss methods to compute the **Mean Deviation** for three types of series:

· Individual Data Series

· Discrete Data Series

· Continuous Data Series

__Individual Data Series__

__Individual Data Series__

When data is given on individual basis. Following is an example of individual series:

Items | 5 | 10 | 20 | 30 | 40 | 50 | 60 | 70 |

__Discrete Data Series__

__Discrete Data Series__

When data is given alongwith their frequencies. Following is an example of discrete series:

Items | 5 | 10 | 20 | 30 | 40 | 50 | 60 | 70 |

Frequency | 2 | 5 | 1 | 3 | 12 | 0 | 5 | 7 |

__Continuous Data Series__

__Continuous Data Series__

When data is given based on ranges alongwith their frequencies. Following is an example of continous series:

Items | 0-5 | 5-10 | 10-20 | 20-30 | 30-40 |

Frequency | 2 | 5 | 1 | 3 | 12 |