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Math Help - For a positive data trend, why am I getting negative coefficients?

  1. #1
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    Exclamation For a positive data trend, why am I getting negative coefficients?

    Hi:

    This is prbably a dumb qu, but I am fitting data in EXCEL. The data trend is positive, but when I use a cubic or quad polynomial to fit the data, I get an equation that has some negative coefficients. Why is this and is there a way of ensuring all positive coefficients? Thanks a lot!!!
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by Annette83 View Post
    Hi:

    This is prbably a dumb qu, but I am fitting data in EXCEL. The data trend is positive, but when I use a cubic or quad polynomial to fit the data, I get an equation that has some negative coefficients. Why is this and is there a way of ensuring all positive coefficients? Thanks a lot!!!
    There is no requirement for the coefficients to all be positive in this situation. So the question becomes why do you require them to be positive.

    CB
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