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  1. M

    Help with simple stat formula

    No 97.5% After two rounds 95%, three 92.7%, etc. What scares me is that it takes 27 rounds (i.e. more than two years) to see the chance of never having been analysed drop under 50% ! Picking 2.5% of the population is obviously not enough.
  2. M

    Help with simple stat formula

    Actually it does: I did a simulation and a comparison with the results of a weighted decision tree. Why doesn't it "quite look right" ? Any rationale behind that ? What am I missing ? Thinking about it, it is like repeatedly picking balls from a urn (e.g. 5 black balls and 195 white balls) and...
  3. M

    Help with simple stat formula

    no, it is purely random and independent. Is this ok ? p(X=k)=(k,n) 0.975^k x 0.025^(n-k) with n number of months and k number of time an element has been analysed over that period of time so in my case k=0 and I am left with p(X=0)=0.025^n Is that right ? (not so...
  4. M

    Help with simple stat formula

    Dear all, I am doing a presentation on a medico-legal issue and I would like to show the probability of an event over time. It has been ages since I last used statistics and I am a bit rusty, to say the least... 2.5% of a large population (50K) is analysed every month. What is the probability...