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    This is my method

    SQRT [ 1^2 + 2^2 + 3^2 - (1+2+3)^2 ]

    I get the wrong answer I dont know why ?
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    (Original post by IShouldBeRevising_)


    This is my method

    SQRT [ 1^2 + 2^2 + 3^2 - (1+2+3)^2 ]

    I get the wrong answer I dont know why ?
    Don't you think the probabilities might be useful?
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    (Original post by BabyMaths)
    Don't you think the probabilities might be useful?
    Oh yeah I was just going of the s.d formula the exam solution guy used in his vid...

    s.d = sqrt ( sum x^2 - x bar squared )
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    (Original post by IShouldBeRevising_)
    Oh yeah I was just going of the s.d formula the exam solution guy used in his vid...

    s.d = sqrt ( sum x^2 - x bar squared )
    You need \displaystyle \sqrt{E(X^2)-E(X)^2}

    and

    \displaystyle E(X)=\sum xP(X=x)
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    (Original post by BabyMaths)
    You need \displaystyle \sqrt{E(X^2)-E(X)^2}

    and

    \displaystyle E(X)=\sum xP(X=x)
    Oh yes its just clicked...

    S.d = sqrt of var (X)

    Nice one

    Was looking at the wrong section on exam solutions so got confused lol
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    Find the variance and square root it.
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    (Original post by BabyMaths)
    You need \displaystyle \sqrt{E(X^2)-E(X)^2}

    and

    \displaystyle E(X)=\sum xP(X=x)
    Hey I have this other small question if you could please help...



    The first part I thought the srcc would be positive as there is a relation ship between the variables as the distance travelled increases the satifsafction decreasses however the answer is -1?
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    The ranks are

    1 2 3 4 5 6 7
    7 6 5 4 3 2 1

    This gives a result of r_s=-1.

    If the ranks were

    1 2 3 4 5 6 7
    1 2 3 4 5 6 7

    then this would give r_s=1.
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    (Original post by BabyMaths)
    The ranks are

    1 2 3 4 5 6 7
    7 6 5 4 3 2 1

    This gives a result of r_s=-1.

    If the ranks were

    1 2 3 4 5 6 7
    1 2 3 4 5 6 7

    then this would give r_s=1.
    ohhh... I see thank you
 
 
 
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