Bollinger Bands
Bollinger Bands are volatility based bands used to help identify situations where prices are too high, or too low, on a relative bases. When prices reach or rise above the upper band, they are too high. When prices reach or drop below the lower band, they are too low. Bollinger bands are calculated by first smoothing the typical price using the MA type and period specified. The typical price for each bar is defined as (high + low + close)/3. The standard deviation is then calculated for the series of typical prices.