A box contains 12 items out of which 4 are defective. A person selects 6 items from the box. The expected number of defective items out of his selected items is
The distribution for which mode does not exist is
If X ~ Exp(5), then the probability density function of X is
The coefficient of variation of Poisson distribution with mean 4 is
The characteristic function of Poisson distribution is
The skewness in a binomial distribution will be zero, if