Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Conditional Epectation of Multinomial

  1. Dec 10, 2014 #1
    So I'm trying to find E(X1,X2|Xn) where X1,X2,.....Xn are the numbers of cell observations in a multinomial distribution.

    How do I even calculate this? I know it is not independent so I cannot split it.

    Does it have something to do with the fact that E(Xi)=nPi ?
  2. jcsd
  3. Dec 10, 2014 #2

    Stephen Tashi

    User Avatar
    Science Advisor

    Intuitively, we would expect the distribution of [itex](X1, X2| Xn = 6) [/itex] to be a multinomial distribution for 6 less objects with the cell probabilities for [itex] X1, X2,..X[n-1] [/itex] scaled by a factor so they sum to 1. I don't know what your notation [itex] E(X1,X2...[/itex] means. Are you asking about a vector of expectations?
  4. Dec 11, 2014 #3
    Interesting. Makes sense.

    Well, E(X1,X2) is just expectation of x1 and x2
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Conditional Epectation of Multinomial