Bollinger Bands: Construction, Price Signals, and Volatility Interpretation

Summary

This article explains Bollinger Bands as a moving average surrounded by upper and lower bands set a chosen number of standard deviations away. It walks through a small closing-price example and gives a second illustrative calculation using a 20-period average and standard deviation. Band width is presented as a way to observe changing volatility: widening bands indicate more variation, while narrowing bands may accompany consolidation.

The article describes several common interpretations: touching an outer band may suggest an extended move, crossing the middle average may signal a change in direction, and prices staying near one band may reflect persistent strength or weakness. These are presented as possible readings rather than tested rules. No backtest or empirical performance evidence is supplied, and the article cautions that the indicator alone is insufficient for trading decisions. It recommends checking other information, such as RSI and volume, to confirm signals.

Key ideas

• Bollinger Bands place standard-deviation boundaries around a moving average.
• The distance between the bands can be used to monitor changes in price volatility.
• Outer-band touches and middle-band crosses are offered as possible signals, not guaranteed reversals or trend changes.
• Persistent proximity to one band may reflect continued directional strength or weakness.
• The article provides illustrative calculations but no performance tests, and recommends using other evidence alongside the indicator.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.