What is Skewness coefficient?
Also known as: skewness
An indicator measuring how asymmetric a distribution is around its mean. In a symmetric distribution (for example, the normal distribution) it equals zero, and the mean and median coincide. With positive skewness the right "tail" of the distribution is long: a few very large values pull the mean above the median. With negative skewness it is the opposite: the left tail is long. The practical conclusion: if skewness is strong, the median is more reliable than the mean for showing the "typical" value.
Source: Skewness (Wikipedia)