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From |
John Antonakis <john.antonakis@unil.ch> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Interpretation of Curvilinear Effects |

Date |
Tue, 09 Jun 2009 20:42:43 +0200 |

Hi:

Or try this after you fit the model: predictnl y_hat= 1.89 + _b[x]*x + _b[x^2]*x^2 , ci(yhat_left yhat_right) twoway (connect y_hat yhat_left yhat_right x, sort) Instead of 1.89 above, put in the estimate of your intercept. HTH, J. ____________________________________________________ Prof. John Antonakis Associate Dean Faculty of Business and Economics University of Lausanne Internef #618 CH-1015 Lausanne-Dorigny Switzerland Tel ++41 (0)21 692-3438 Fax ++41 (0)21 692-3305 Faculty page: http://www.hec.unil.ch/people/jantonakis&cl=en Personal page: http://www.hec.unil.ch/jantonakis ____________________________________________________ On 09.06.2009 20:31, Christian Weiss wrote:

Dear Statalisters, I am currently evaluating curvilinear effects of the variable X on Y by standard OLS. To asses the curvilinearity I generated X^2 and X^3 and included these variables stepwise in the regressions. Looking at the significance levels and the signs of the coefficients I concluded the following: if X and X^2 is significant: -> X has a positive sign and X^2 has a negative sign: Bell Shaped -> X has a negative sign and X^2 has a positive sign: U Shaped However, the last regression analysis yielded significant X and X^2, but both with the same sign. I am struggling how to interpret this effect. Any help is highly appreciated! :) Best regards Chris * * 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/

* * 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/

**Follow-Ups**:**Re: st: Interpretation of Curvilinear Effects***From:*Richard Williams <Richard.A.Williams.5@ND.edu>

**References**:**st: Interpretation of Curvilinear Effects***From:*Christian Weiss <christian.weiss@nightberry.de>

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