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Question about random numbers

  1. Jul 14, 2009 #1
    I have recently come across the 80/20 rule... I am using the Pareto Distribution's pdf to generate some dataset that I wanted... Now if I have a set of 50 items and I need to generate 40% of these items 60% of the times, how am I supposed to go about doing this? I know how to select items with certain probabilities but this task is confusing me... Anyone has some inputs for me please?
  2. jcsd
  3. Aug 6, 2009 #2


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    One way is to create duplicate (multiplicate) items until you reach the desired proportion, then use a uniform rule to select.

    For example, if I had 2 items {x, y} and wanted to obtain x 67% of the time, I'd duplicate x once, and make draws from the set {x, x, y}.
  4. Aug 6, 2009 #3
    To select one of m items, from a total of n items, a proportion y of the time, you need to select each of the m items with probability y/m, and each of the remaining n-m items with probability (1-y)/(n-m)
    Last edited: Aug 6, 2009
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