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Probability of birthdays on every day

  1. Feb 2, 2012 #1
    Please may someone help me with this and if you have an answer please may you show all the steps that you took. This is not a prep question but I was thinking about it and wondering what the answer was but my statistics skills are not good enough for this yet. :)

    If I have a randomly selected group of 430 people. What is the probability that there is 1 birthday on ever single day in the year? (Assume that it is a 365 day year)

  2. jcsd
  3. Feb 2, 2012 #2
    Good luck...I guess you are asking for an answer from the purely mathematical point of view assuming a uniform distribution of births throughout the year?

    I am wondering because that's not what REALLY happens. Weather and holidays affect love-making; last I heard, new year's is a 'lucky' day and so, we have a lot of September people.

    Just look at the animal kingdom; ok, they don't have holidays, but look at how the times when, basically, the entire group gives birth within a matter of days or weeks ruled by migratory patterns, availability of food, weather conditions, etc.

    Anyway, just a thought.
  4. Feb 2, 2012 #3
    Yeh I am looking for an answer with a mathematical point of view that assumes that births are evenly distributed throughout the year.
  5. Feb 2, 2012 #4
    This is the "Coupon Collector's Problem". See my reply to this post


    for a formula for the probability.
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