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Math Help - Set notation/ a bit cheeky

  1. #1
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    Jan 2010
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    Set Notation denoting events

    Hey guys just having some trouble with set notation.

    A survey is classified as successful if usable data is obtained from it. Let Ai denote the event that at most i repetitions of the survey are required for success. Use set notation to identify the following events:
    a) Exactly 1 repetition is required for success
    b) At least 2 repetitions are required for success,
    c) At least i (where i ≥2) repetitions are required for success
    d) Exactly i (where i ≥2) repetitions are required for success
    e) Is it true that A1OR A2 = A2?
    f) What then is A1AND A2AND A3?
    Ok so I am pretty sure that e is true because A1 is a proper subset of A2? Therefore the union of them would be equal to just the elements of A2
    For a I know that A1 is a subset of all the successive sets and so I would need to negate the subsets from the subsequent sets but I am not sure how to do this. Something along the lines of Ai = (i:i=1)? A friend of mine said something about A1 OR (A0)c
    For b I am not sure at all the best I could do was A2ORÖAi = (i:i>2)
    For c it might be Big ORi Ai = (i:i≥2)
    D and f I donít really have any idea.

    I know the difference between exactly and at least but am not sure how to apply it in this problem. I have this horrible feeling that everything I just wrote is wrong haha

    If someone could steer me in the right direction that would be great.

    (Iím new to set notation) Should there be a different variable in the brackets?
    Last edited by jonnyh; March 3rd 2010 at 03:50 AM.
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