Kurtosis is the fourth moment of the distribution of the standardized (z) values. It is a measure of the outlier (rare, extreme observation) character of the distribution as compared with the normal, Gaussian distribution.

The normal distribution has a kurtosis of 0.

Positive kurtosis indicates that the distribution is more outlier-prone than the normal distribution, while negative kurtosis indicates that the distribution is less outlier-prone than the normal distribution.