Free Online Lean Six Sigma Encyclopedia

English |  Español |  Français |  Português |  Deutsch |  中文

Skewness

Go Back

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 = Mo, Median = Md, Mean = Mn

External Links

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