Super fast question about finding the mean and variance of a random variable

Hi, if a problem gave you F(x) = x + 2, x > 0

Would you derive F(x) to get f(x) in order to solve for its mean and variance?

Thank you for your time.

Re: Super fast question about finding the mean and variance of a random variable

"Given F(x)= x+ 2, x> 0" doesn't **mean** anything! What is F supposed to be? It can't be a probability function because it has values larger than 1 and it can't be a probability density because its integral has values larger than 1.

Re: Super fast question about finding the mean and variance of a random variable

Sorry I wrote up an example function without really thinking.

How about this probability distribution function?

F(x) = 1 - x , x> 0