These alerts report each time the stock price moves an integer number of standard deviations from the closing price.  These are very similar to the % up/down for the day alerts, but these are based on volatility rather a percentage.  For some stocks it is interesting and unusual when they move up by less than 1% from the previous close.  Others must move by 2% or more before they are interesting.  The user can require higher standards, as described below.

These alerts are slightly different from our other volatility alerts, because these use a more traditional formula for volatility.  For most of our alerts we use two weeks worth of volume-weighted, intraday volatility data, and we scale it so that "1" means a typical move for one 15 minute period.  These alerts are based on a year's worth of volatility data.  Recent data is weighted more heavily than year old data, and the data is scaled so that "1" means a standard deviation for one day.