|Sharpening Your Trading Skills: Using Bollinger Bands
By Jim Wyckoff
The Bollinger Bands (B-Bands) technical study was created by John Bollinger, the president of Bollinger Capital Management Inc., based in Manhattan Beach, California. Bollinger is well respected in the futures and equities industries.
Traders generally use B-Bands to determine overbought and oversold zones, to confirm divergences between prices and other technical indicators, and to project price targets. The wider the B-bands on a chart, the greater the market volatility; the narrower the bands, the less market volatility.
B-Bands are lines plotted on a chart at an interval around a moving average. They consist of a moving average and two standard deviations charted as one line above and one line below the moving average. The line above is two standard deviations added to the moving average. The line below is two standard deviations subtracted from the moving average.
Some traders use B-Bands in conjunction with another indicator, such as the Relative Strength Index (RSI). If the market price touches the upper B-band and the RSI does not confirm the upward move (i.e. there is divergence between the indicators), a sell signal is generated. If the indicator confirms the upward move, no sell signal is generated, and in fact, a buy signal may be indicated.
If the price touches the lower B-band and the RSI does not confirm the downward move, a buy signal is generated. If the indicator confirms the downward move, no buy signal is generated, and in fact, a sell signal may be indicated.
Another strategy uses the Bollinger Bands without another indicator. In this approach, a chart top occurring above the upper band followed by a top below the upper band generates a sell signal. Likewise, a chart bottom occurring below the lower band followed by a bottom above the lower band generates a buy signal.
B-Bands also help determine overbought and oversold markets. When prices move closer to the upper band, the market is becoming overbought, and as the prices move closer to the lower band, the market is becoming oversold.
Importantly, the marketís price momentum should also be taken into account. When a market enters an overbought or oversold area, it may become even more so before it reverses. You should always look for evidence of price weakening or strengthening before anticipating a market reversal.
Bollinger Bands can be applied to any type of chart, although this indicator works best with daily and weekly charts. When applied to a weekly chart, the Bands carry more significance for long-term market changes. John Bollinger says periods of less than 10 days do not work well for B-Bands. He says that the optimal period is 20 or 21 days.
Like most computer-generated technical indicators, I use B-Bands as mostly an indicator of overbought and oversold conditions, or for divergence--but not as a specific generator of buy and sell signals for my trading opportunities. It's just one more "secondary" trading tool, as opposed to my "primary" trading tools that include chart patterns and trend lines and fundamental analysis.
By Jim Wyckoff, contributing to Kitco News; email@example.com