What is Bollinger Bands(BB) indicator, the instructions of Bollinger Bands(BB) and how to use the Bollinger Bands(BB) indicator, the calculation of Bollinger Bands(BB) indicator and the Bollinger Bands(BB) indicator main paramete
Bollinger Bands Technical Indicator (BB) is similar to Envelopes. The only difference is that the bands of Envelopes are plotted a fixed distance (%) away from the moving average, while the Bollinger Bands are plotted a certain number of standard deviations away from it. Standard deviation is a measure of volatility, therefore Bollinger Bands adjust themselves to the market conditions. When the markets become more volatile, the bands widen and they contract during less volatile periods.
Bollinger Bands are usually plotted on the price chart, but they can be also added to the indicator chart (Custom Indicators). Just like in case of the Envelopes, the interpretation of the Bollinger Bands is based on the fact that the prices tend to remain in between the top and the bottom line of the bands. A distinctive feature of the Bollinger Band indicator is its variable width due to the volatility of prices. In periods of considerable price changes (i.e. of high volatility) the bands widen leaving a lot of room to the prices to move in. During standstill periods, or the periods of low volatility the band contracts keeping the prices within their limits.
Bollinger Bands consist of a middle band with two outer bands. The middle band is a simple moving average that is usually set at 20 periods. A simple moving average is used because the standard deviation formula also uses a simple moving average. The look-back period for the standard deviation is the same as for the simple moving average. The outer bands are usually set 2 standard deviations above and below the middle band.
The following traits are particular to the Bollinger Band:
- abrupt changes in prices tend to happen after the band has contracted due to decrease of volatility.
- if prices break through the upper band, a continuation of the current trend is to be expected.
- if the pikes and hollows outside the band are followed by pikes and hollows inside the band, a reverse of trend may occur.
- the price movement that has started from one of the band’s lines usually reaches the opposite one. The last observation is useful for forecasting price guideposts.
Bollinger bands are formed by three lines. The middle line (ML) is a usual Moving Average.
ML = SUM [CLOSE, N]/N
The top line, TL, is the same as the middle line a certain number of standard deviations (D) higher than the ML.
TL = ML + (D*StdDev)
The bottom line (BL) is the middle line shifted down by the same number of standard deviations.
BL = ML — (D*StdDev)
- N — is the number of periods used in calculation;
- SMA — Simple Moving Average;
- StdDev — means Standard Deviation.
StdDev = SQRT(SUM[(CLOSE — SMA(CLOSE, N))^2, N]/N)
It is recommended to use 20-period Simple Moving Average as the middle line, and plot top and bottom lines two standard deviations away from it. Besides, moving averages of less than 10 periods are of little effect.
W-Bottoms were part of Arthur Merrill’s work that identified 16 patterns with a basic W shape. Bollinger uses these various W patterns with Bollinger Bands to identify W-Bottoms. A "W-Bottom" forms in a downtrend and involves two reaction lows. In particular, Bollinger looks for W-Bottoms where the second low is lower than the first, but holds above the lower band. There are four steps to confirm a W-Bottom with Bollinger Bands. First, a reaction low forms. This low is usually, but not always, below the lower band. Second, there is a bounce towards the middle band. Third, there is a new price low in the security. This low holds above the lower band. The ability to hold above the lower band on the test shows less weakness on the last decline. Fourth, the pattern is confirmed with a strong move off the second low and a resistance break.
M-Tops were also part of Arthur Merrill’s work that identified 16 patterns with a basic M shape. Bollinger uses these various M patterns with Bollinger Bands to identify M Bottoms. According to Bollinger, tops are usually more complicated and drawn out than bottoms. Double tops, head-and-shoulders patterns and diamonds represent evolving tops.
In its most basic form, an M-Top is similar to a double top. However, the reaction highs are not always equal. The first high can be higher or lower than the second high. Bollinger suggests looking for signs of non-confirmation when a security is making new highs. This is basically the opposite of the W-Bottom. A non-confirmation occurs with three steps. First, a security forges a reaction high above the upper band. Second, there is a pullback towards the middle band. Third, prices move above the prior high, but fail to reach the upper band. This is a warning sign. The inability of the second reaction high to reach the upper band shows waning momentum, which can foreshadow a trend reversal. Final confirmation comes with a support break or bearish indicator signal.
Moves above or below the bands are not signals per se. As Bollinger puts it, moves that touch or exceed the bands are not signals, but rather "tags". On the face of it, a move to the upper band shows strength, while a sharp move to the lower band shows weakness. Momentum oscillators work much the same way. Overbought is not necessarily bullish. It takes strength to reach overbought levels and overbought conditions can extend in a strong uptrend. Similarly, prices can "walk the band" with numerous touches during a strong uptrend. Think about it for a moment. The upper band is 2 standard deviations above the 20-period simple moving average. It takes a pretty strong price move to exceed this upper band. An upper band touch that occurs after a Bollinger Band confirmed W-Bottom would signal the start of an uptrend. Just as a strong uptrend produces numerous upper band tags, it is also common for prices to never reach the lower band during an uptrend. The 20-day SMA sometimes acts as support. In fact, dips below the 20-day SMA sometimes provide buying opportunities before the next tag of the upper band.
Bollinger Bands reflect direction with the 20-period SMA and volatility with the upper/lower bands. As such, they can be used to determine if prices are relatively high or low. According to Bollinger, the bands should contain 88-89% of price action, which makes a move outside the bands significant. Technically, prices are relatively high when above the upper band and relatively low when below the lower band. However, relatively high should not be regarded as bearish or as a sell signal. Likewise, relatively low should not be considered bullish or as a buy signal. Prices are high or low for a reason. As with other indicators, Bollinger Bands are not meant to be used as a stand alone tool. Chartists should combine Bollinger Bands with basic trend analysis and other indicators for confirmation.
- Upper Line: The top line, TL
- Lower Line: The bottom line, BL
- Period: Averaging period to calculate the main line, default is 20
- Deviation: Deviation from the main line, default is 2
- Shift: The indicator shift relative to the chart, default is 0
- Apply to: Applied price
- Median Price, (high+low)/2
- Typical Price, (high+low+close)/3
- Weighted Close, (high+low+close+close)/4