Probability distribution of the future stock price












1












$begingroup$


I have this exercise to do:



Consider a stock with an initial price of $40, an expected return of 16% per annum and a volatility of 20% per annum. Find the probability distribution of the future stock price in 6 months' time. Determine the 95% confidence of interval.



$S_0=40$



$mu=0.16$



$sigma=0.20$



$T=0.5$



Using the lognormal property of stock prices $(ln{S_T}approxvarphileft[ln{S_0}+left(mu-frac{sigma^2}{2}right)T, sigma^2Tright]$, I have $ln{S_T}approxvarphileft[3.759, 0.02right]$.



The results of the textbook says "there is a 95% probability that a normally distributed variable has a value within 1.96 standard deviaton of its mean."



Viewing another topic from this forum, I found this possible solution: $P[lnS_T>ln95]=1−P[lnS_T<ln95]=1−P[Z<z=frac{ln95-3.759}{sqrt{0.02}}]$
If I want to compute $z$, as result I will have $z=5.62$. Thus, $N(5.62)=1$ (is not possible for this exercise).



Supposing a 95% c.i. I can't solve the problem. Is anyone can explain me how can I approach it?



I would be beyond thankful for any help and advice.










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$endgroup$












  • $begingroup$
    "$textrm{The results of the textbook says "there is a 95% probability that a normally distributed ...}$" This statement just means that $P(-1.96 leq Z leq 1.96)=0.95$, where $Zsim mathcal N(0,1)$
    $endgroup$
    – callculus
    Dec 7 '18 at 19:32






  • 1




    $begingroup$
    Thank you, now I've understood my mistake
    $endgroup$
    – Martina Marty
    Dec 7 '18 at 19:41










  • $begingroup$
    That makes me happy. You´re welcome.
    $endgroup$
    – callculus
    Dec 7 '18 at 19:43
















1












$begingroup$


I have this exercise to do:



Consider a stock with an initial price of $40, an expected return of 16% per annum and a volatility of 20% per annum. Find the probability distribution of the future stock price in 6 months' time. Determine the 95% confidence of interval.



$S_0=40$



$mu=0.16$



$sigma=0.20$



$T=0.5$



Using the lognormal property of stock prices $(ln{S_T}approxvarphileft[ln{S_0}+left(mu-frac{sigma^2}{2}right)T, sigma^2Tright]$, I have $ln{S_T}approxvarphileft[3.759, 0.02right]$.



The results of the textbook says "there is a 95% probability that a normally distributed variable has a value within 1.96 standard deviaton of its mean."



Viewing another topic from this forum, I found this possible solution: $P[lnS_T>ln95]=1−P[lnS_T<ln95]=1−P[Z<z=frac{ln95-3.759}{sqrt{0.02}}]$
If I want to compute $z$, as result I will have $z=5.62$. Thus, $N(5.62)=1$ (is not possible for this exercise).



Supposing a 95% c.i. I can't solve the problem. Is anyone can explain me how can I approach it?



I would be beyond thankful for any help and advice.










share|cite|improve this question











$endgroup$












  • $begingroup$
    "$textrm{The results of the textbook says "there is a 95% probability that a normally distributed ...}$" This statement just means that $P(-1.96 leq Z leq 1.96)=0.95$, where $Zsim mathcal N(0,1)$
    $endgroup$
    – callculus
    Dec 7 '18 at 19:32






  • 1




    $begingroup$
    Thank you, now I've understood my mistake
    $endgroup$
    – Martina Marty
    Dec 7 '18 at 19:41










  • $begingroup$
    That makes me happy. You´re welcome.
    $endgroup$
    – callculus
    Dec 7 '18 at 19:43














1












1








1





$begingroup$


I have this exercise to do:



Consider a stock with an initial price of $40, an expected return of 16% per annum and a volatility of 20% per annum. Find the probability distribution of the future stock price in 6 months' time. Determine the 95% confidence of interval.



$S_0=40$



$mu=0.16$



$sigma=0.20$



$T=0.5$



Using the lognormal property of stock prices $(ln{S_T}approxvarphileft[ln{S_0}+left(mu-frac{sigma^2}{2}right)T, sigma^2Tright]$, I have $ln{S_T}approxvarphileft[3.759, 0.02right]$.



The results of the textbook says "there is a 95% probability that a normally distributed variable has a value within 1.96 standard deviaton of its mean."



Viewing another topic from this forum, I found this possible solution: $P[lnS_T>ln95]=1−P[lnS_T<ln95]=1−P[Z<z=frac{ln95-3.759}{sqrt{0.02}}]$
If I want to compute $z$, as result I will have $z=5.62$. Thus, $N(5.62)=1$ (is not possible for this exercise).



Supposing a 95% c.i. I can't solve the problem. Is anyone can explain me how can I approach it?



I would be beyond thankful for any help and advice.










share|cite|improve this question











$endgroup$




I have this exercise to do:



Consider a stock with an initial price of $40, an expected return of 16% per annum and a volatility of 20% per annum. Find the probability distribution of the future stock price in 6 months' time. Determine the 95% confidence of interval.



$S_0=40$



$mu=0.16$



$sigma=0.20$



$T=0.5$



Using the lognormal property of stock prices $(ln{S_T}approxvarphileft[ln{S_0}+left(mu-frac{sigma^2}{2}right)T, sigma^2Tright]$, I have $ln{S_T}approxvarphileft[3.759, 0.02right]$.



The results of the textbook says "there is a 95% probability that a normally distributed variable has a value within 1.96 standard deviaton of its mean."



Viewing another topic from this forum, I found this possible solution: $P[lnS_T>ln95]=1−P[lnS_T<ln95]=1−P[Z<z=frac{ln95-3.759}{sqrt{0.02}}]$
If I want to compute $z$, as result I will have $z=5.62$. Thus, $N(5.62)=1$ (is not possible for this exercise).



Supposing a 95% c.i. I can't solve the problem. Is anyone can explain me how can I approach it?



I would be beyond thankful for any help and advice.







probability normal-distribution finance






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 7 '18 at 19:30







Martina Marty

















asked Dec 7 '18 at 19:17









Martina MartyMartina Marty

225




225












  • $begingroup$
    "$textrm{The results of the textbook says "there is a 95% probability that a normally distributed ...}$" This statement just means that $P(-1.96 leq Z leq 1.96)=0.95$, where $Zsim mathcal N(0,1)$
    $endgroup$
    – callculus
    Dec 7 '18 at 19:32






  • 1




    $begingroup$
    Thank you, now I've understood my mistake
    $endgroup$
    – Martina Marty
    Dec 7 '18 at 19:41










  • $begingroup$
    That makes me happy. You´re welcome.
    $endgroup$
    – callculus
    Dec 7 '18 at 19:43


















  • $begingroup$
    "$textrm{The results of the textbook says "there is a 95% probability that a normally distributed ...}$" This statement just means that $P(-1.96 leq Z leq 1.96)=0.95$, where $Zsim mathcal N(0,1)$
    $endgroup$
    – callculus
    Dec 7 '18 at 19:32






  • 1




    $begingroup$
    Thank you, now I've understood my mistake
    $endgroup$
    – Martina Marty
    Dec 7 '18 at 19:41










  • $begingroup$
    That makes me happy. You´re welcome.
    $endgroup$
    – callculus
    Dec 7 '18 at 19:43
















$begingroup$
"$textrm{The results of the textbook says "there is a 95% probability that a normally distributed ...}$" This statement just means that $P(-1.96 leq Z leq 1.96)=0.95$, where $Zsim mathcal N(0,1)$
$endgroup$
– callculus
Dec 7 '18 at 19:32




$begingroup$
"$textrm{The results of the textbook says "there is a 95% probability that a normally distributed ...}$" This statement just means that $P(-1.96 leq Z leq 1.96)=0.95$, where $Zsim mathcal N(0,1)$
$endgroup$
– callculus
Dec 7 '18 at 19:32




1




1




$begingroup$
Thank you, now I've understood my mistake
$endgroup$
– Martina Marty
Dec 7 '18 at 19:41




$begingroup$
Thank you, now I've understood my mistake
$endgroup$
– Martina Marty
Dec 7 '18 at 19:41












$begingroup$
That makes me happy. You´re welcome.
$endgroup$
– callculus
Dec 7 '18 at 19:43




$begingroup$
That makes me happy. You´re welcome.
$endgroup$
– callculus
Dec 7 '18 at 19:43










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