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From |
"Martin Weiss" <martin.weiss1@gmx.de> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: Re: fracpoly model question |

Date |
Fri, 13 Mar 2009 02:40:01 +0100 |

<>

HTH Martin _______________________

To: <statalist@hsphsun2.harvard.edu> Sent: Friday, March 13, 2009 12:16 AM Subject: st: fracpoly model question

I am using stata 9.2. Here are the coefficient estimates from my _fracpoly_analysis:study1twsg Coef. Std. Err. t P>t [95% Conf. Interval] Itemp__1 15093.12 4454.121 3.39 0.012 4560.802 25625.45 Itemp__2 -10666.18 3136.84 -3.40 0.011 -18083.63 -3248.734 Itemp__3 1945.114 569.9302 3.41 0.011 597.4436 3292.785 _cons .0053322 .0008244 6.47 0.000 .0033828 .0072815 Deviance: -113.24. Best powers of temp among 164 models fit: -2 -2 -2. Fractional polynomial model comparisons: temp df Deviance Res. SD Gain P(term) Powers Not in model 0 -101.249 .002545 -- -- Linear 1 -101.599 .002641 0.000 0.603 1 m = 1 2 -101.796 .002617 0.197 0.714 3 m = 2 4 -104.278 .00248 2.679 0.508 3 3 m = 3 6 -113.237 .001764 11.638 0.196 -2 -2 -2so, given these coefficients and my 'x' having a value of 25, I think mylinear regression equation for predicting y should be:y=.0053322+(15093.12*25^-2)+(-10666.18*25^-2*log(25))+1945.114*25^-2*(log(25))^2if this is correct, the equation is not yielding the same estimates as_fracpred_. The above equation returns an answer of 1.467, while_fracpred_ (which I believe is correct) gives 0.003.What am I doing wrong? thanks a bunch in advance, Chrisp.s. I know I'm not supposed to reply to a different thread with a newquestion, but I've tried to send this message twice as a new message andit has not gotten through.* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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**References**:**st: fracpoly model question***From:*Chris Witte <eljefespeaks@yahoo.com>

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