1. Let X~Pois(1) what is the variance of X given x is bigger than 0?
I've tried to use the conditional variance formula but I had problems with calculating the
probability of x=k and x>0.
2. A worker calls his wife once a day. the length of each talk is independent of the others, its a random variable which distributes exponentially with a mean of 5.
One day the boss tells the worker that it is unacceptable and he has 3 more chances, if he calls his wife and talks for more than 10 minutes 3 times he will be fired.
What is the expected number of days the worker has before he gets fired?
d. e^2 + e^3
The parameter of the exponential distribution is 1/5... this is easy.
but I have no idea what should I do next.