Hi

The following question i don't understand why my answer is incorrect.

X is an exponential rc, with mean 2. What is the Pr(X < 2.5)?

My answer is

$\displaystyle F(x) = 1$ - e^($\displaystyle \lambda x$)

$\displaystyle \lambda = 2$ and x = 2.5

so $\displaystyle 1 $ - e^(-2*2.5)

P.S