[Bollinger Band] is mean deviation same as standard deviation?

[ghost]

I am trying to make a bollinger band indicator in jstock editor. Currently I am trying to create the upper line using this formula

Upper line = SMA(20)+2*20-day-Standard deviation

the problem is i cant find a standard deviation from the editor option instead i got Mean deviation.
Are both same or different?
my indicator http://i.imgur.com/IR4oiNa.png

[RandallSell]

Hi PotHead,

No Standard Deviation is NOT the same as Mean Deviation, although with the correct numbers they would come out the same. The STD would never be a negative number, whereas the MD could be a negative value.

This might help a bit:
http://www.investopedia.com/ask/answers/021215/what-difference-between-standard-deviation-and-average-deviation.asp

And yes, i can't find an STD function either - weird that it doesn't have it. So alas you are probably stuck doing it the hard way by doing the calc yourself. Having said that, I don't recall seeing a square-root function either so if that is missing you would be SOL.

-randall

[ghost]

Hi RandallSell ,
Thank you for the comment. It seems I cant calculate standard deviation in jstock. Jstock editor lacks many math function like square root, log, exponential etc. Now i have to find another way :(

Once more thanks man for the quick info 💯