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http://quotes.barchart.com/techrept.asp?sym=ge 
 
It gave 8.98% Historic volatility. 
 
I'm new to options, but what do you need this for? Email privately 
 
thanks 
 
tony 
qitrader
 
 On 8/7/05, Phsst <phsst@xxxxxxxxx> wrote:
Been playing with HV Calcs this weekend using following AFL code: 
 
per = Param( "Volatility Period", 20, 2, 365 ); 
days = Param("History days in Calc", 252,1,365);  
Plot(100*StDev(log(C/Ref(C,-1)),per)*sqrt(days),"Volatility",3,1); 
 
NOTE: 'days' default represents number of trading days in year rather 
than calendar days. (Don't split hairs about anything between 250 and 
256, since none of those values changes things much) 
 
Example code was applied to GE daily chart and yields an HV 20day  
result of 8.98457 using default Params. 
 
I've researched enough to feel comfortable with the formula and Params 
which were posted on this forum quite a long time ago. 
 
But when I go to three (3) different web sites which are reputed to be 
'expert' sites, I see three different values for current Historical 
Volatility (all of which differ from my calculated result). 
 
www.optionclub.com shows HV 20day value of 12.0 
www.optionstrategist.com shows HV 20day value of 10 
www.ivolatility.com shows HV 20day value of 13.74 
 
Beats me how a universally accepted formula can yield such a diverse 
set of results. 
 
Anyone see anything obvious? 
 
 
 
 
 
  
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