Algebraic sum of the deviations(d) of a set of values from their arithmetic mean is zero
but when we find the mean deviation about mean .we have to again find Algebraic sum of the deviations(d) of a set of values from their arithmetic mean .but in this case it isnt zero.
why
but when we find the mean deviation about mean .we have to again find Algebraic sum of the deviations(d) of a set of values from their arithmetic mean .but in this case it isnt zero.
why
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You are RIGHT.
In case of the calculation of mean deviation. we ignore the algebraic sign (+ / - ) of the deviations. In other words the magnitude of the deviations of items is taken BUT not their direction. As such, whether the sum is zero or NOT is immaterial.
For the purpose of taking deviations we prefer Median to Mean, because of the mathematical property of the Median "that the sum of deviations of items taken from Median ignoring the algebraic sign is always minimum"
In case of the calculation of mean deviation. we ignore the algebraic sign (+ / - ) of the deviations. In other words the magnitude of the deviations of items is taken BUT not their direction. As such, whether the sum is zero or NOT is immaterial.
For the purpose of taking deviations we prefer Median to Mean, because of the mathematical property of the Median "that the sum of deviations of items taken from Median ignoring the algebraic sign is always minimum"