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Pita Bollinger
Dari Wikipedia bahasa Indonesia, ensiklopedia bebas
(Dialihkan dari Bollinger bands)
Contoh Pita Bollinger dengan periode 10 hari dan rentang 2 deviasi standar
Grafik Bollinger atau lebih dikenal dengan nama Bollinger Bands adalah merupakan salah satu indikator dalam analisis teknis ( analisa untuk membaca pergerakan pasar melalui grafik) yang ditemukan oleh John Bollinger pada tahun 1980an. Grafik Bolinger ini merupakan pengembangan dari konsep pita perdagangan yang dapat digunakan untuk mengukur batas ketinggian ataupun batas kerendahan dari pada harga saham secara relatif terhadap harga sebelumnya.
Grafik Bollinger terdiri dari :
- Garis tengah yang merupakan periode N dari pergerakan sederhana.
- Garis atas pada K kali Periode N standar deviasi diatas garis menengah
- Garis bawah pada K kali Periode N standar deviasi dibawah garis menengah
Nilai khusus untuk N dan K masing-masing adalah 20 dan 2, respectively.
Penggunaan grafik Bollinger
Grafik Bollinger ini tidak dapat digunakan secara berdiri sendiri tanpa menggunakan indikator lainnya seperti misalnya dengan menggunakan indikator Indeks Kekuatan Relatif atau lebih dikenal dengan nama Relative Strength Index (RSI). Dengan menggunakan grafik Bollinger dengan RSI ini maka dapat diperoleh suatu indikator jual atau beli misalnya :
- Apabila RSI diatas angka 80 dan apabila grafik Bollinger menyempit serta harga cenderung mendatar, maka pada kondisi seperti ini apabila RSI membentuk sinyal bearish divergencemaka adalah merupakan suatu momentum tepat untuk menjual.
- Apabila RSI di dibawah angka 20, dan apabila grafik Bollinger menyempit serta harga cenderung datar, maka pada kondisi ini apabila RSI membentuk bullish divergence maka adalah saat yang baik untuk melakukan pembelian.
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Bollinger Bands
Bollinger Bands Defined
Bollinger Bands is a versatile tool combining moving averages and standard deviations and is one of the most popular technical analysis tools available for traders. There are three components to the Bollinger Band indicator:
- Moving Average: By default, a 20-period simple moving average is used.
- Upper Band: The upper band is usually 2 standard deviations (calculated from 20-periods of closing data) above the moving average.
- Lower Band: The lower band is usually 2 standard deviations below the moving average.
Bollinger Bands (in blue) are shown below in the chart of the E-mini S&P 500 Futures contract:
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Playing the Bollinger Bands
Playing the bands is based on the premise that the vast majority of all closing prices should be between the Bollinger Bands. That stated, then a stock's price going outside the Bollinger Bands, which occurs very rarely, should not last and should "revert back to the mean", which generally means the 20-period simple moving average. A version of this strategy is discussed in the book Trade Like a Hedge Fund by James Altucher.
Buy Signal
In the example shown in the chart below of the E-mini S&P 500 Future, a trader buys or buys to cover when the price has fallen below the lower Bollinger Band.
Sell Signal
The sell or buy to cover exit is initiated when the stock, future, or currency price pierces outside the upper Bollinger Band.
These buy and sell signals are graphically represented in the chart of the E-mini S&P 500 Futures contract shown below:
More Conservative Playing the Bands
Rather than buying or selling exactly when the price hits the Bollinger Band, the more aggressive approach, a trader could wait and see if the price moves above or below the Bollinger Band and when the price closes back inside the Bollinger Band, then the trigger to buy or sell short occurs. This helps to reduce losses when prices breakout of the Bollinger Bands for a while. However, many profitable opportunities would be lost. To illustrate, the chart of the E-mini S&P 500 Future above shows many missed opportunities. However, in the chart on the next page, the more conservative approach would have prevented many painful losses.
Also, some traders exit their long or short entries when price touches the 20-day moving average.
A different, and quite polar opposite way to use Bollinger Bands is described on the next page, Playing Bollinger Band Breakouts.
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Bollinger Band Breakouts
Basically the opposite of "Playing the Bands" and betting on reversion to the mean is playing Bollinger Band breakouts. Breakouts occur after a period of consolidation, when price closes outside of the Bollinger Bands. Other indicators such as support and resistance lines (see: Support & Resistance) can prove beneficial when deciding whether or not to buy or sell in the direction of the breakout.
The chart of Wal-Mart (WMT) below shows two such Bollinger Band breakouts:
Bollinger Band Breakout through Resistance Buy Signal
Price breaks above the upper Bollinger Band after a period of price consolidation. Other confirming indicators are suggested, such as resistance being broken in the chart above of Wal-Mart stock.
Bollinger Band Breakout through Support Sell Signal
Price breaks below the lower Bollinger Band. It is suggested that other confirming indicators be used, such as a support line being broken, such as in the example above of Wal-Mart stock breaking below support.
This strategy is discussed by the man who created Bollinger Bands, John Bollinger.
Bollinger Bands can also be used to determine the direction and the strength of the trend. The chart below of the E-mini S&P 500 Futures contract shows a strong upward trend:
Bollinger Band Showing a Strong Trend
The chart above of the E-mini S&P 500 shows that during a strong uptrend, prices tend to stay in the upper half of the Bollinger Band, where the 20-period moving average (Bollinger Band centerline) acts as support for the price trend.
The reverse would be true during a downtrend, where prices would be in the lower half of the Bollinger Band and the 20-period moving average would act as downward resistance.
Bollinger Bands adapt to volatility and thus are useful to options traders, specifically volatility traders. The next page describes how to use Bollinger Bands to make better options trades.
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Option Volatility Strategies
There are two basic ways to trade volatility:
- Buy options with low volatility in hopes that volatility will increase and then sell back those options at a higher price.
- Sell options with high volatility in hopes that volatility will decrease and then buy back those same options at a cheaper price.
Since Bollinger Bands adapt to volatility, Bollinger Bands give options traders a good idea of when options are relatively expensive (high volatility) or when options are relatively cheap (low volatility). The chart below of Wal-Mart stock illustrates how Bollinger Bands can be used to trade volatility:
Buy Options when Volatility is Low
When options are relatively cheap, such as in the center of the chart above of Wal-Mart when the Bollinger Bands significantly contracted, buying options, such as a straddle or strangle, might be a good options strategy.
The reasoning is that after sharp moves, prices tend to stay in a trading range to rest. After prices have rested, such as periods when the Bollinger Bands are extremely close together, then prices usually will begin to move once again. Therefore, buying options when Bollinger Bands are tight together, might be a smart options strategy.
Sell Options when Volatility is High
At times when options are relatively expensive, such as in the far right and far left of the chart above of Wal-Mart when the Bollinger Bands were significantly expanded, selling options in the form of a straddle, strangle, or iron condor, might be a good options strategy to use.
The logic is that after prices have risen or fallen significantly, such as periods when the Bollinger Bands are extremely far apart, then prices usually will begin to consolidate and become less volatile. Hence, selling options when Bollinger Bands are far apart, potentially could be a smart options volatility strategy.
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