Kurtosis is a property of a probability function which describes how well that function matches the bell curve. If you have a bell curve, you should be able to measure the values in the middle of the curve, the most common values, and use these to predict the extreme parts of the curve, the special cases. Kurtosis describes probability curves, like those often found in the stock market, where the special cases occur more or less often than would be predicted by the common cases.
Our alerts are based on separating the normal variations in stock prices from the interesting variations. It is important to understand the kurtosis of a stock graph in order to know what is truly unusual.