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OCR (Not MEI) S1 May 12 Exam Discussion.

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    How did everyone find it? Personally thought it was harder than previous papers!
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    I found it really hard! It started off okay and then slowly got worse on the last page
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    swear it's the hardest there has been, even the first question was harder than usual. do you know what you were meant to do for the let question? with the sum to infinity?
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    (Original post by studentforum111)
    swear it's the hardest there has been, even the first question was harder than usual. do you know what you were meant to do for the let question? with the sum to infinity?
    I got something like 0.513 or something like that.
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    A lot of my pupils have been saying similar things about it being the hardest S1 paper that they have seen - I haven't seen it so I couldn't possibly say.
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    Was it the sum to infinity of a Geometric Distribution?
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    I personally thought it was okay But I didn't really do any past papers so I don't know how it compares to previous ones
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    I thought it went ok, the arrangements question tripped me up a bit though.

    For the sum to infinity question I made a sequence of every other time, so it was something like p + pq^2 + pq^4 .... Then used the formula, subbing all the values in. I'm not sure if that's correct though.
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    (Original post by Tomming)
    Was it the sum to infinity of a Geometric Distribution?
    I think so yes.

    Definitely messed this exam up. Personally, Core 2 went better and that's saying something because I thought stats was going to help my maths grade as it's always been my best module
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    (Original post by AspiringDoctor)
    I think so yes.

    Well the sum to infinity of the probabilities in a geometric distribution should be 1, as only a sum to infinity will take into account all possible outcomes of a geometric distibution and therefore they would have to total 1.
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    (Original post by Tomming)
    Was it the sum to infinity of a Geometric Distribution?
    yes

    but i got -2, which im guessing is wrong
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    is mr m puttin up answers?
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    (Original post by Crowseph)
    I thought it went ok, the arrangements question tripped me up a bit though.

    For the sum to infinity question I made a sequence of every other time, so it was something like p + pq^2 + pq^4 .... Then used the formula, subbing all the values in. I'm not sure if that's correct though.
    That sounds right, they've used that sort of thing before, I did that method and it made sense
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    (Original post by Crowseph)
    For the sum to infinity question I made a sequence of every other time, so it was something like p + pq^2 + pq^4 .... Then used the formula, subbing all the values in. I'm not sure if that's correct though.
    X~Geo(\frac1{20})

    Yeah the probability of it being on a half hour was P(X=1)+P(X=3)+P(X=5)+...
    which is p+pq^2+pq^4+pq^6+...

    so it's just a g.p. with a=p=\frac{1}{20} and r=q^2={\frac{19}{20}}^2

    then you just do S_\infty=\frac{a}{1-r} :P
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    I found it really hard! I have never done a harder paper. How do you do the standard deviation question!? :confused:
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    (Original post by ht4)
    is mr m puttin up answers?
    maaaaan i hope so.
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    (Original post by TheServersAre)
    X~Geo(\frac1{20})

    Yeah the probability of it being on a half hour was P(X=1)+P(X=3)+P(X=5)+...
    which is p+pq^2+pq^4+pq^6+...

    so it's just a g.p. with a=p=\frac{1}{20} and r=q^2={\frac{19}{20}}^2

    then you just do S_\infty=\frac{a}{1-r} :P
    Yeah that's exactly what I did it was just like a past paper question
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    Is there going to be an unofficial mark scheme for this? I'm really nervous! I think it went OK but the mark schemes always make me feel better :P

    By the way I got something like 0.513 for the last question too. A was 1/20, and R was (19/20)^2.
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    (Original post by ht4)
    is mr m puttin up answers?
    Nope, he no do stats =( And yeah I got the 0.513.. just after the exam :/ spent 20mins on that xD I would say that's far harder than usual. Also a lot more discussion of this going on in the "revision" thread,
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    difficult paper, anyone know answers to the arranging / combination questions? got 10/11 for the last one of them but I don't think it's right.

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