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Thread: Incidence rate in population and in random sample

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    Incidence rate in population and in random sample




    How can I anser a question like the following:

    When the true incidence rate of an event in the population is "X" (say, 12%), how likely is it that the event is observed at least once in a random sample of "Y" (say, 250) subjects drawn from this population?

    Thank you very much!

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    Re: Incidence rate in population and in random sample


    If you can assume that the probability of the event is the same for each individual (unrealistic in life, but convenient and simple nonetheless), you can rely on the binomial distribution, with parameter p = 0.12, and n = 250 trials.

    To simplify things, you could note that P(Z \geq 1) = 1 - P(Z = 0) and just focus on computing P(Z = 0), where Z is the number of subjects with the event in the sample of 250.
    Last edited by ab-stats; 08-25-2016 at 04:25 PM.

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