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Thread: Power function - finding if the slope is significant or not?

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    Question Power function - finding if the slope is significant or not?




    Hi,

    I'm using power functions to look at a relationship between time and age and I need to be able to test whether or not the slope of this relationship is significant or not. I am using SYSTAT, but cannot find out how to run this and produce a p-value.

    Is this not possible to test at all? Any alternatives can think of to test whether slope of a power function is significant or not??

    Any help would be great
    Cheers

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    Re: Power function - finding if the slope is significant or not?

    Here's an example of one output from running non-linear regression for function ( y = z * x^k )

    All I need to do is find out whether this slope is significantly different from 0. Am unsure of how to go about testing this

    Sum of Squares and Mean Squares
    Source:________/...SS............./df.... /Mean Squares
    Regression______/ 42.162539 __/2 ___/21.081269
    Residual________/ 0.385111 __/5 ___/0.077022
    Total___________/ 42.54765 ___/7
    Mean corrected___/0.649023 ___/6

    Parameter____Estimate____ASE____Parameter/ASE____ Wald 95% Confidence Interval
    _______________________________________________Lower_______Upper
    K__________18.475309___20.882025___0.884747____-35.203645____72.154264
    Z__________-0.274805___0.154224___-1.781853____-0.67125____0.121641

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    Re: Power function - finding if the slope is significant or not?


    if a power function is y = a x^b then what is the slope?

    Loglinearize perhaps: log y = log a + b log x test significance in linear model ... otherwise use non-linear regression ...

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