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Accuracy of Bollinger Band Standard Deviations, especially in current circumstances Rate this Topic:
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traderlady
Posted : Monday, January 15, 2018 2:50:49 PM
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Joined: 10/7/2004
Posts: 1,178

Bruce, I noticed on July 3, 2017 in following a discussion about Real Motion, you said:

 

"...assuming you want the moving average to stay mostly within the Bollinger Bands...the 50 period simple moving average of Real Motion isn't "normal" in the statistical sense.

 

"If the data distribution were approximately normal then about 68% of values would fall within the Bollinger Bands with the Std Dev set  to 1.00, 95% with SD set to 2.00 and 99.7% with SD set to 3.00.

 

"Instead, the SMA50 is generally on either a fairly steady uptrend or a fairly steady downtrend. Except during the transitions from SMA50 moving up to down and vice versa, the most recent value is usually the highest value during the period covered by the BB or the lowest value during the period.

 

"This means you would probably want to set your Std Dev to about 1.3 if you wanted the SMA50 to ride just inside the Bollinger Bands on its way up and down."

 

You also said, "...the 50 period simple moving average is a lot smoothing than Real Motion itself, so the Bollinger Bands of the 40 period simple moving average is going to be a lot more stable with a lot less width than if applied to the Real Motion directly."

 

MY QUESTIONS:

 

1)  Does your recommendation of Std Dev 1.3 only apply to use with a Real Motion formula?

 

2)  Does this only apply to Bollinger Bands 40 for the reasons you stated above?

 

3)  Although I realize this may be proprietary, can you provide or approximate a Real Motion formula?

 

4) Do the data distribution percentages mentioned above result from statistical back-testing over a certain period of time? 

 

5) How many years -- or how much time?

 

6)  If the idea of a "Melt Up" in the stock market (that we hear about from the business media) continues, would this require a re-testing of Bollinger Band deviations over a shorter period of time given the change in circumstances attributed investors reacting to a reduction of tax changes for corporations and the supposition that corporate money will flow back into the US from other countries?"

 

Looking forward to your responses.

Bruce_L
Posted : Tuesday, January 16, 2018 12:31:15 PM


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Joined: 10/7/2004
Posts: 65,138

The 1.3 is related to Bollinger Bands of period 40 and a steady rise (or fall). This is just the width at which the price (or other indicator) to which the Bollinger Bands are applied would line up when rising or falling at a steady rate.

This width can change a bit based on period. The CCI Clone & Bollinger Bands topic explores this in greater detail.

The percentage of data which falls within Bollinger Bands is based on statistics. It applies to something called "normal distribution". This is a statistical term which applies to data distributed ino a "bell curve". It does not apply to stock data because stock data is not normally distributed. It was not experimentally derived from stock data and just based on the underlying math.

I cannot make any suggestions as to adjustments you might want to make to an indicator for specific market conditions or about how to interpret an indicator.

I have sent you a copy of me interpretation of the RealMotion indicator via TCMail.

How to Receive Messages with TC Mail



-Bruce
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HarleyBD
Posted : Tuesday, January 29, 2019 5:07:06 PM
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Joined: 6/30/2014
Posts: 60

Hi Bruce,

Could you please send me a copy of me interpretation of the RealMotion indicator via TCMail.

Best regards,

HarleyBD

bcochrane
Posted : Wednesday, January 30, 2019 7:48:57 AM
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Joined: 9/17/2010
Posts: 484

If I could trouble you for the Real Motion implementation

Thank you

HarleyBD
Posted : Wednesday, January 30, 2019 3:02:03 PM
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Joined: 6/30/2014
Posts: 60

Thank you Bruce for your quick response.  I'll be testing with this code this evening and won't need to shovel snow (I'll be working like a dog, close to the fireplace).

Best regards,

HarleyBD

 

Priyaa
Posted : Wednesday, February 6, 2019 12:47:17 PM
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Joined: 1/11/2019
Posts: 28

Can you please send me this in TCMail?

Thank you

Bruce_L
Posted : Wednesday, February 6, 2019 1:00:01 PM


Worden Trainer

Joined: 10/7/2004
Posts: 65,138

I have sent you a copy of me interpretation of the RealMotion indicator via TCMail.



-Bruce
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