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Risk 1 - Hans Buehler

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Modeling <strong>Risk</strong> – Basics<br />

Black & Scholes<br />

• The formula is understood as<br />

Change of<br />

option value<br />

Change of<br />

Delta position<br />

value<br />

FV( t<br />

dt,<br />

S(<br />

t<br />

dt))<br />

FV( t,<br />

S(<br />

t))<br />

dFV(<br />

t)<br />

=<br />

=<br />

(<br />

t,<br />

S(<br />

t))<br />

<br />

S(<br />

t<br />

(<br />

t)<br />

dS(<br />

t)<br />

dt)<br />

S(<br />

t)<br />

<br />

• Practitioners often look at ―cash delta‖ rather than delta.<br />

It reflects the cash value of the delta position:<br />

— This gives<br />

<br />

$<br />

( t) : =<br />

dFV(<br />

t,<br />

S(<br />

t))<br />

=<br />

(<br />

t)<br />

S(<br />

t)<br />

<br />

$<br />

dS(<br />

t)<br />

( t)<br />

S(<br />

t)<br />

Return on the<br />

stock<br />

investment<br />

11

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