Definition

A measure of the lack of symmetry of a distribution. The formula for skewness is shown here, where Y-Bar is the mean, s is the standard deviation and N is the number of data points in the sample.

A positive value for skewness indicates that the data are skewed right, meaning that the right tail is "heavier", pulling the mean to the right of the median. Conversely, a negative value for skewness indicates that the data are skewed left.Symmetric distributions (such as the Normal distribution) will have a skewness value close to zero.Examples

Mode = M_{o}, Median = M_{d}, Mean = M_{n
}

External Links

NIST Statistics Handbook: Measures of Skewness and Kurtosis - http://www.itl.nist.gov/div898/handbook/eda/section3/eda35b.htm