If X∼Poisson(λ)X \sim Poisson(\lambda)X∼Poisson(λ), what is the coefficient of variation (CVCVCV) defined as σ/μ\sigma/\muσ/μ?
λ\lambdaλ
λ\sqrt{\lambda}λ
1/λ1/\sqrt{\lambda}1/λ
1/λ1/\lambda1/λ