Next section: Kurtosis

Skew can be calculated as:

where μ is the mean and σ is the standard deviation.

The normal distribution has a skew of 0 since it is a symmetric distribution.

As a general rule, the mean is larger than the median in positively skewed distributions and less than the median in negatively skewed distributions.(Click here for an illustration.) There are counter examples. For example it is not uncommon for the median to be higher than the mean in a postively skewed bimodal distribution or with discrete distributions. See "Mean, Median, and Skew: Correcting a Textbook Rule" by Paul Hippel, for more details.

Click here for an interaction demonstration.

Next section: Kurtosis