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I understand that there is a "stdev" function built into the AFL but it seems as if this is a moving standard deviation....I include a small piece of an example I came across on the net ...what this person is explaining here is exactly what I whish to apply to a price graph....please help with the transformation to AFL !
To understand how standard deviation is calculated, let's work through a couple of very basic examples. We'll use two families, the Smithsand the Joneses. Both families have three children, and for both families,the average age of the children is 10. However, the range of the children's ages is quite different for the two families. The Smiths have an eight year old daughter, a 10 year old son, and a 12 year old daughter. The Joneseshave a one-year old son, a nine year old daughter, and a 20-year-old son. Both sets of children have the same average age, but we can use standard deviation to measure the variance around that mean, or average.
To calculate standard deviation, we first find the average of the children. We then subtract each child's age from the average age. Then, we square the resulting number. (By squaring the numbers, we eliminate any negative numbers from the equation.) For the Smith family, we end up with:
We then add these numbers together, divide by the total number of children, and take the square root of the whole thing:
I have manually applied these formulas to an Excel spreadsheet and found a big difference between the "stdev" graph in AB and the graph in the spreadsheet....I also have a book about unit trust that lists all unit trust in detail and also provides a small graph on the deviations, I tested my spreadsheet against a few of these printed graphs and found them to be the same, but different than the one's in AB....thus I assume there must be another kind of standard deviation calculation for AB like in the example above.
If I'm understanding the concept of Standard Deviations wrong, than please except my apologies for this question.
Kind regards
Louw Coetzer
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<DIV><FONT face=Arial><STRONG><EM>Tomasz</EM></STRONG></FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>I understand that there is a "stdev" function built
into the AFL but it seems as if this is a moving standard deviation....I include
a small piece of an example I came across on the net ...what this person is
explaining here is exactly what I whish to apply to a price graph....pleasehelp
with the transformation to AFL !</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>
<TABLE border=0 cellPadding=0 cellSpacing=0 width=605>
<TBODY>
<TR align=left vAlign=top>
<TD colSpan=3 height=227 width=605>
<TABLE border=0 cellPadding=0 cellSpacing=1>
<TBODY>
<TR align=left vAlign=top>
<TD height=225 width=359>
<P><FONT color=#0000ff
face="Times New Roman,Times,Times NewRoman">To understand how
standard deviation is calculated, let's work through a couple of
very basic examples. We'll use two families, the Smiths and the
Joneses. Both families have three children, and for both families,
the average age of the children is 10. However, the range of the
children's ages is quite different for the two families. The Smiths
have an eight year old daughter, a 10 year old son, and a 12 year
old daughter. The Joneses have a one-year old son, a nine year old
daughter, and a 20-year-old son. Both sets of children have thesame
average age, but we can use standard deviation to measure the
variance around that mean, or average.</FONT></P>
<P><FONT color=#0000ff><FONT
face="Times New Roman,Times,Times NewRoman">To calculate standard
deviation, we first find the average of the children. We then
subtract each child's age from the average age. Then, we squarethe
resulting number. (By squaring the numbers, we eliminate any
negative numbers from the equation.) For the Smith family, we end up
with:<BR></FONT> </FONT></P></TD></TR></TBODY></TABLE></TD></TR>
<TR align=left vAlign=top>
<TD height=10 width=244><IMG border=0 height=1
src="cid:002c01c1396d$ece47c20$01ffbac4@xxxx"; width=244></TD>
<TD width=244><IMG border=0 height=1
src="cid:002c01c1396d$ece47c20$01ffbac4@xxxx"; width=244></TD>
<TD width=117><IMG border=0 height=1
src="cid:002c01c1396d$ece47c20$01ffbac4@xxxx"; width=117></TD></TR>
<TR align=left vAlign=top>
<TD colSpan=2 height=25></TD>
<TD align=left rowSpan=2 vAlign=top width=117><IMG alt=equations border=0
height=71 src="cid:002d01c1396d$ecec1d40$01ffbac4@xxxx";
width=89></TD></TR>
<TR align=left vAlign=top>
<TD height=73></TD>
<TD align=left vAlign=top width=244><IMG alt="Average age" border=0
height=30 src="cid:002e01c1396d$ecec1d40$01ffbac4@xxxx";
width=217></TD></TR>
<TR align=left vAlign=top>
<TD colSpan=3 height=47 width=605>
<TABLE border=0 cellPadding=0 cellSpacing=1>
<TBODY>
<TR align=left vAlign=top>
<TD width=243> </TD>
<TD height=45 width=359>
<P><FONT color=#0000ff><FONT
face="Times New Roman,Times,Times NewRoman">We then add these
numbers together, divide by the total number of children, and take
the square root of the whole
thing:<BR></FONT> </FONT></P></TD></TR></TBODY></TABLE></TD></TR>
<TR align=left vAlign=top>
<TD colSpan=3 height=15></TD></TR>
<TR align=left vAlign=top>
<TD height=66></TD>
<TD align=left colSpan=2 vAlign=top width=361><IMG
alt="Standard Deviation" border=0 height=37
src="cid:002f01c1396d$ecec1d40$01ffbac4@xxxx";
width=278></TD></TR></TBODY></TABLE></FONT></DIV>
<DIV><FONT face=Arial size=2>I have manually applied these formulas to an Excel
spreadsheet and found a big difference between the "stdev" graph in AB and the
graph in the spreadsheet....I also have a book about unit trust that lists all
unit trust in detail and also provides a small graph on the deviations, I tested
my spreadsheet against a few of these printed graphs and found them to be the
same, but different than the one's in AB....thus I assume there must be another
kind of standard deviation calculation for AB like in the example
above.</FONT></DIV>
<DIV> </DIV>
<DIV align=center><FONT face=Arial size=2><EM>If I'm understanding the concept
of Standard Deviations wrong, than please except my apologies for this
question.</EM></FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Kind regards</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2>Louw Coetzer</FONT></DIV></BODY></HTML>
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