Subject CT6, April 2013, Question 8

Discussion in 'CS2' started by Molly, Sep 16, 2022.

  1. Molly

    Molly Ton up Member

    Hi Guys,

    What is the distribution of N is this question? i would have assumed poisson, but the mean and var arent the same once we have computed them from the conditional formulae

    Thanks
    Molly
     
  2. Andrew Martin

    Andrew Martin ActEd Tutor Staff Member

    Hi Molly

    N is a Poisson RV but the parameter is treated as a random variable. So:

    N | mu = a ~ Poi(a)
    or
    N | mu ~ Poi(mu)

    The unconditional moments (eg E[N] = E[E[N| mu]] can be calculated using the formulae on page 16 of the Tables.

    Hope this helps

    Andy
     
    Molly likes this.

Share This Page