百度知道: .comview wiki: tion key points: 1,事件以固定的平均瞬时速率 (或称密度)λ随机且独立地出现时,那么这个事件在单位时间(面积或体积)内出现的次数或个数就近似地服从泊松分布. 2,它是一种离散型概率分布.若随机变量 x 只取非负整数值,取k值的概率为 (k=0,1,2..;e) where e is the base of the nat ral logarithm (e = 2....) k is the n mber of occ rrences of an event - the probability of which is given by the f nction k! is the factorial of k λ is a positive real n mber, eq al to the expected n mber of occ rrences d ring the given interval. for instance, if the events occ r on average 4 times per min te, and one is interested in the probability of an event occ rring k times in a 10 min te interval, one wo ld se a poisson distrib tion as the model with λ = 10×4 = 40. 3,泊松分布的期望和方差均为 λ .泊松分布的参数λ是单位时间(或单位面积)内随机事件的平均发生率. 4,物理含义:泊松分布适合于描述单位时间内随机事件发生的次数.如某一服务设施在一定时间内到达的人数,电话交换机接到呼叫的次数,汽车站台的候客人数,机器出现的故障数,自然灾害发生的次数等等.