MEAN DEVIATION

Mean  deviation of a series is the arithmetic  average of the  deviations of various  items  from the  median  or mean  of that series.

Median is preferred since the sum  of the deviations from the median  is less than the  from  the mean. So the values of  mean deviation calculation from  median  is usually  less than that  calculated from mean.

Mean  deviation is known  as first Moment  of Dispersion.

Coefficient of mean  deviation from  mean = Mean Deviation ( M. D)/  Arithmetic  Mean

Coefficient  of mean deviation from  median = Mean Deviation (M. D.)/ Median

Coefficient  of mean deviation from  mode = Mean Deviation( M. D)/ Mode