1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Conditional expected value

  1. May 19, 2013 #1
    we have a variable that takes values 1,...,6 with density:
    n 1 2 3 4 5 6
    f(n) 0.1 0.2 0.1 0.3 0,176 0,124

    What is the average price (expected value) of X under the condition that X is even?

    E(X/X=even)=k*P(X=k/X=even)=0.2*2+4*0.3+0.124*6
    i am doing this but its says its not correct what i am doing wrong in the type?
     
  2. jcsd
  3. May 19, 2013 #2

    I like Serena

    User Avatar
    Homework Helper

    Use the product rule:

    P(X=k|X even) = P(X=k) P(X even)
     
  4. May 19, 2013 #3
    P(X even) here is 1/2? or 1/3?
     
  5. May 19, 2013 #4

    I like Serena

    User Avatar
    Homework Helper

    P(X even) = P(X=2 or X=4 or X=6)

    Use the sum rule for mutually exclusive events:

    P(A or B) = P(A) + P(B) if A and B are mutually exclusive.
     
  6. May 19, 2013 #5
    P(X=2)=0.2? from the table?
     
  7. May 19, 2013 #6

    I like Serena

    User Avatar
    Homework Helper

  8. May 19, 2013 #7
    but its says that its not correct my answer... i find this 1.462656 in the final answer
     
  9. May 19, 2013 #8

    I like Serena

    User Avatar
    Homework Helper

    What did you calculate then?
     
  10. May 19, 2013 #9
    first i found this P(X=2 OR X=4 OR X=6)=0.624
    AND E(X/X=even)=k*P(X=k/X=even)=0.2*2*0.624+0.624*4*0.3+0.124*6*0.624...=1.4626
     
  11. May 19, 2013 #10

    I like Serena

    User Avatar
    Homework Helper

    Oops. My mistake.
    The rule is: P(X=k|X even) = P(X=k) / P(X even)
     
  12. May 19, 2013 #11
    k*(P(X=k)/P(X even)) like this?
     
  13. May 19, 2013 #12

    I like Serena

    User Avatar
    Homework Helper

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Conditional expected value
  1. Expected value (Replies: 8)

  2. Expected value (Replies: 10)

  3. Expected value (Replies: 7)

Loading...