[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

st: Interpretation of Curvilinear Effects

From   Christian Weiss <>
Subject   st: Interpretation of Curvilinear Effects
Date   Tue, 9 Jun 2009 20:31:43 +0200

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
*   For searches and help try:

© Copyright 1996–2022 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index