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    can someone kindly explain how i answer this question (in attachment) im very confused and dont know how to solve it.

    so far i done:

    \frac{100-108}{standard  deviation}=0.03

    but what is the 0.03 and how do i go from here on.

    all help appreciated

    thanks
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    (Original post by 95_alim)
    can someone kindly explain how i answer this question (in attachment) im very confused and dont know how to solve it.

    so far i done:

    \frac{100-108}{standard  deviation}=0.03

    but what is the 0.03 and how do i go from here on.

    all help appreciated

    thanks
    Take the Z value of 0.97 and put a - sign


    \frac{100-108}{standard  deviation}=-1.881

    I could be wrong, let someone else confirm what I've done.
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    (Original post by Azland)
    Take the Z value of 0.97 and put a - sign


    \frac{100-108}{standard  deviation}=-1.881

    I could be wrong, let someone else confirm what I've done.

    ok but can u tell me why its -1.88 and not 1.88?

    you maybe right in your working.
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    (Original post by 95_alim)
    ok but can u tell me why its -1.88 and not 1.88?

    you maybe right in your working.
    -Z = 1 - P(Z)

    You want the value for 3% so in that case 1 - P(97) = 3%

    Also, if you notice in your question that if you took a positive Z, your SD would be negative which isnt possible.
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    (Original post by Azland)
    -Z = 1 - P(Z)

    You want the value for 3% so in that case 1 - P(97) = 3%

    Also, if you notice in your question that if you took a positive Z, your SD would be negative which isnt possible.
    hmm kinda makes sense
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    can anyone confirm if the answer provided is correct?
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    (Original post by 95_alim)
    can anyone confirm if the answer provided is correct?
    Why dont you just check the mark scheme or the answer sheet from wherever you got the question from.
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    a) working out the standard deviation:

    The general formula is usually
    Z = (X - mean) divided by the standard deviation.

    0.03 is basically the Probability of jars having contents weighing less than 100 grams (3% as they said in the question)

    From the question we know that:
    X = 100g
    Mean = 108g
    Probability = 0.03

    So now we need to know the Z value...
    You can find this out using a Z value calculator on the Internet or from a table of values given to you from your textbook maybe. The Z value for 0.03 = -1.880792

    So now plug in your numbers into the formula:
    -1.880792 = (100 - 108)/standard deviation

    Then re-arrange to get your standard deviation:

    Standard deviation = (100 - 108)/-1.880792

    And that should give you your answer

    Hope that helps
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    (Original post by dz287)
    a) working out the standard deviation:

    The general formula is usually
    Z = (X - mean) divided by the standard deviation.

    0.03 is basically the Probability of jars having contents weighing less than 100 grams (3% as they said in the question)

    From the question we know that:
    X = 100g
    Mean = 108g
    Probability = 0.03

    So now we need to know the Z value...
    You can find this out using a Z value calculator on the Internet or from a table of values given to you from your textbook maybe. The Z value for 0.03 = -1.880792

    So now plug in your numbers into the formula:
    -1.880792 = (100 - 108)/standard deviation

    Then re-arrange to get your standard deviation:

    Standard deviation = (100 - 108)/-1.880792

    And that should give you your answer

    Hope that helps

    yh has definitely helped.

    thanks
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    (Original post by 95_alim)
    yh has definitely helped.

    thanks
    I guess he confirmed my answer
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    (Original post by 95_alim)
    yh has definitely helped.

    thanks
    No Problem ^^
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    does anyone have the OCR AS jan 2012 S1 paper and mark scheme by any chance?

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Updated: April 21, 2012
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