ADAPT Probability Problem

mardi 20 janvier 2015

The following is an adapt question:

Assume the Black-Scholes framework.



The continuously compounded risk-free interest rate is r.



The price of the stock is S. The stock pays continuously compounded dividends at a rate of 4% per year. The stock’s volatility is \sigma. The continuously compounded expected return on the stock is r+\sigma^{2}.



A 3-month, K-strike European call option on the stock has a delta of 0.68.



Calculate the probability that the stock price is above K at the end of 3 months.





I am confused about why this probability would be equal to N(d2-hat).

The answer key and formula sheet states that P(S>k)=N(d2-hat). I trust this is correct. However, I thought it should be N(d1-hat) because of the way All-or-Nothing Options are explained. Ie, you use N(d1) (+d1 if S>K and -d1 if S<K) for the S portion since S is not fixed, but N(d2) for the K portion since K is a constant. This formula seems inconsistent (or to conflict with) the formulas for all-or-nothing options.



Can anybody explain why d2 is appropriate here? Furthermore, what does N(d1) or N(d2) really represent?



Thanks for any input!





ADAPT Probability Problem

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