Novice Traderís Notebook: Bollinger Bands by Amy Wu
Bollinger Bands were created by market technician John Bollinger. They are a branch of envelope analysis and use standard deviations in calculation instead of a fixed percentage. Bollinger Bands are displayed as three bands. The middle band normally consists of a moving average of 20 days. The upper band is derived by adding two standard deviations to the middle band. The lower band is found by subtracting two standard deviations from the middle band.