Mean Deviation

Mean Deviation

In order to find the dispersion of values of x from a central value ‘a’, they find the deviations about a. To calculate the mean need know the sum of the deviations. & number of observations.

Also mean of deviations = Sum of deviations
Number of observations
Find the mean of deviations about mean is not of any use , as far as the measure of dispersion is concerned. Keep in mind find an appropriate measure of dispersion, they need the distance of each value from a central tendency or a fixed number ‘a’. The absolute value of the difference of two numbers give the distance between the numbers when represented on a number line. To find the measure of dispersion from a fixed number ‘a’ then take the mean of the absolute values of the deviations from the central value. This mean is called the ‘mean deviation’. Thus mean deviation about a central value ‘a’ is the mean of the absolute values of the deviations of the observations from ‘a’. The mean deviation from ‘a’ is denoted as M.D. (a). Therefore,

M.D. (a) = Sum of absolute values of deviations from 'a '
Number of observations

Mean deviation obtained from any measure of central tendency. However, mean deviations from mean & median are often used in statistical studies.

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Conditional probability

Factors of 21