Say $X(t),t\geq 0,$ denotes a Brownian motion process with drift parameter $\mu=3$ and variance parameter $\sigma^2 = 9$. If $X(0)=10$ I want to find
- $E[X(2)]$
- $Var[X(2)]$
- $P(X(2)>20)$
My reasoning is the following: Since the Brownian motion has a Gaussian probability density with mean $t\mu$ and variance $t\sigma^2$, I would say that
- $E[X(2)] = 2\times 3 = 6$
- $Var[X(2)] = 2\times 9 = 18$
- $P(X(2)>20) = \int_{20}^\infty{\frac{1}{6\sqrt{2\pi}}e^{-(x-6)^2/36}dx}$
Is my reasoning correct?