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In page Skewness:

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where Q is the quantile function (i.e., the inverse of the cumulative distribution function). The numerator is difference between the average of the upper and lower quartiles (a measure of location) and the median (another measure of location), while the denominator is the semi-interquartile range ( Q ( 3 / 4 ) Q ( 1 / 4 ) ) / 2 {\displaystyle ({Q}(3/4)}-{{Q}(1/4))/2} , which for symmetric distributions is equal to the MAD measure of dispersion.[citation needed]