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    A bag has 4 counters. 2 are worth £2, 1 is worth £4 and 1 is worth £8.
    (a) You randomly select a counter, gaining £X. Find E(X) and Var(X)
    (b) You place the first counter in your pocket. You then draw a second
    counter from the bag at random. This counter has value £Y . Without further calculations,
    write down Exp(y) and var(y)

    I am not quite sure how to do b, would you have to consider each case seperatly??
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    (Original post by number23)
    I am not quite sure how to do b, would you have to consider each case seperatly??
    No, no calculation is required.

    This may help.

    Imagine you just take a first counter out of the bag, and without looking at it put it in your pocket.

    Then take the second counter. What's the expectation/variance of this second selection.

    I can think of one more scenario that might give a clue, if you're still stuck.
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    (Original post by ghostwalker)
    No, no calculation is required.

    This may help.

    Imagine you just take a first counter out of the bag, and without looking at it put it in your pocket.

    Then take the second counter. What's the expectation/variance of this second selection.

    I can think of one more scenario that might give a clue, if you're still stuck.
    I think the expectation and variance are the same but not sure exactly why, what was ur other example?
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    (Original post by number23)
    I think the expectation and variance are the same but not sure exactly why, what was ur other example?
    Yes they are.

    Put your hand in the bag, pick a coin, but don't pull it out. Let it go, and pick a different coin and pull that one out.
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    (Original post by number23)
    I think the expectation and variance are the same but not sure exactly why, what was ur other example?
    If you are expected to pick a £4 counter, and there is a £4 counter in the bag, what would be the effect if you took it out?
 
 
 
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