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Thread: why the sum of residuals must always equal zero?

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    why the sum of residuals must always equal zero?




    Hello,

    I was wondering why the sum of the residuals of a simple regression line must always equal zero. It simply blows my mind that it could always be true. Please help me wrap my mind around this concept.

    Thanks,
    MofB

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    Re: why the sum of residuals must always equal zero?

    Quote Originally Posted by MarginOfBuffett View Post
    Hello,

    I was wondering why the sum of the residuals of a simple regression line must always equal zero. It simply blows my mind that it could always be true. Please help me wrap my mind around this concept.

    Thanks,
    MofB
    See this post here (note that this question has been posed before):

    http://www.talkstats.com/showthread....ght=#post45548

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    Re: why the sum of residuals must always equal zero?

    Quote Originally Posted by Dragan View Post
    See this post here (note that this question has been posed before):

    http://www.talkstats.com/showthread....ght=#post45548
    ok, so pretty much it boils down to that r(sy/sx) = 0?

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    Re: why the sum of residuals must always equal zero?


    Uh... That's pretty much one of the only terms that doesn't evaluate to 0. \sum(x_i - \bar{x}) is 0 though so when you multiply r(sy/sx) by 0 you get 0.

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