1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Poisson RV

  1. Jun 11, 2009 #1
    The children in a small town own slingshots. In a recent contest 4% of them were such poor shots that they did not hit the target even once in 100 shots. If the number of times a randomly selected child has hit the target is approximately a Poisson random variable, determine the percentage of children who have hit the target at least twice.

    Just want to make sure my reasoning/logic for this is correct...

    so P(X=x) = eλn /n!

    so from the question P(X=0) = 0.04 = e => λ = 3.21887

    Then P(X >= 2) = 1 - ( P(X=0) + P(X=1) ) = 1 - 0.04 - e-3.218873.218871/1!

    I get 0.83

    does this seem reasonable?
  2. jcsd
  3. Jun 11, 2009 #2


    Staff: Mentor

    Yes, it does. I didn't check your numeric calculations, but how you set it up looks correct, and your answer seems reasonable. Since 4% of the kids didn't hit the target in 100 tries, that means 96% hit it one or more times. We would expect that the percentage of kids who hit the target two or more times would be less than 96%, which is what you have.
  4. Jun 11, 2009 #3
    Thanks, just wanted to make sure i had the right idea!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Poisson Date
Poisson's equation in 1D with point source Oct 13, 2017
Statistics probability questions Feb 18, 2017
Maximize winnings game Dec 10, 2016
Poisson summation formula Oct 5, 2016