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Bollinger Bands are drawn at a given number of standard deviations from a moving average of a price. Since standard deviation is a measure of volatility, the bands are self-adjusting: widening during volatile markets and contracting during calmer periods. Bollinger Bands were created by John Bollinger.
Bollinger Bands
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An Envelope is comprised of two moving averages. One moving average is shifted upward and the second moving average is shifted downward.
Envelope
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