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!

Homework Help: Binomial and Hypergeometric Distributions

  1. Nov 4, 2012 #1
    1. The problem statement, all variables and given/known data

    We have an urn with 5 red and 18 blues balls and we pick 4 balls with replacement. We denote the number of red balls in the sample by Y. What is the probability that Y >=3? (Use Binomial Distribution)

    2. Relevant equations


    3. The attempt at a solution

    Okay, so we were asked to use the Binomial Distribution here.

    The whole sample is denoted by N = 23. The number of trials is n = 4 since we have to choose 4 balls from 23. Since Y denotes the number of red balls in the sample and replacement is used, how do we find p? Is it the probability of having 3 red balls and one blues + the probability of 4 red balls? So, (5/23)^3 * (18/23) + (5/23)^4? What is k? Is it in our case 3 and 4?

    I will post the other hypergeometric problem when I solve this. I am not good at statistics in any way so I would appreciate the help.
  2. jcsd
  3. Nov 4, 2012 #2
    compute p(y=k) from the binomial distribution with probabiliyy 5/18 and n=23
  4. Nov 4, 2012 #3
    Okay thanks, but shouldn't p = 5/23? The total number of balls is 23.
  5. Nov 4, 2012 #4
    Yes,of course.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook