The absolute deviation of an element of a data set is the absolute difference between that element and a given point. Typically the deviation is reckoned from the central value, being construed as some type of average, most often the median or sometimes the mean of the data set. Example:
D i = | x i − m ( X ) | {\displaystyle D_{i}=|x_{i}-m(X)|}
where
Di is the absolute deviation,
xi is the data element
and m(X) is the chosen measure of central tendency of the data set—sometimes the mean (
x ¯ {\display style {\overline {x}})
but most often the median.