1. Not finding help here? Sign up for a free 30min 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!

Stats question: Item collection

  1. Sep 24, 2012 #1
    1. The problem statement, all variables and given/known data

    Suppose that I'm collecting cards, and that in a complete collection there are m items.
    When buying a new card, there's an equal probability that the card is any of those m cards.

    Let X be the number of cards I need to buy in order to get a complete collection

    What is the Expectation/Ex of X? What is the Standard Deviation?

    2. Relevant equations

    Let [itex]X = \sum^{m}_{i=1} X_{i} [/itex], where [itex] X_{i} [/itex] is the number of cards I need to buy in order to get a new type of card when I already have i - 1 different types of cards


    3. The attempt at a solution

    I figure this problem would involve probability mass function, but to be honest I'm stuck as I haven't had any probability or stats in over 10 years.

    Any good pointers on how to go on with this problem?
     
  2. jcsd
  3. Sep 24, 2012 #2

    lanedance

    User Avatar
    Homework Helper

    haven't worked it, but say you have n>m cards, then what is the probability of having m different cards might be a place to start...
     
  4. Sep 24, 2012 #3
    After doing some reading, this looks like something that falls under Geometric Distribution. Correct?
     
  5. Sep 24, 2012 #4

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Google the Coupon Collector's Problem.

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




Similar Discussions: Stats question: Item collection
  1. Stats Related Question (Replies: 1)

  2. Stats question (Replies: 4)

  3. Quick Stats question (Replies: 5)

Loading...