A truncated discrete distribution is one in which a particul

A truncated discrete distribution is one in which a particular class cannot be observed and is eliminated from the sample space. In particular, if X has range 0, 1, 2, ... and the 0 class cannot be observed (as is usually the ease), the 0-truncated random variable XT has pdf P(XT =x) = P(X=x) / P(X > 0),x = 1,2, Find the pmf, mean and variance of the 0-truncated Poisson(lambda) random variable.