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From | "L.M.A. Mulotte" <L.Mulotte@uvt.nl> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | RE: st: Shapes of two Inverted U curves (same model on two different samples) |
Date | Tue, 5 Jul 2011 09:16:38 +0000 |
Thank you Maarten. It helps a lot Now, are there any means to graph the two Inverted-U curves on the same graph? Thank for your consideration Best, Louis -----Original Message----- From: Maarten Buis [mailto:maartenlbuis@gmail.com] Sent: Tuesday, July 05, 2011 10:06 AM To: statalist@hsphsun2.harvard.edu Subject: Re: st: Shapes of two Inverted U curves (same model on two different samples) On Tue, Jul 5, 2011 at 9:51 AM, L.M.A. Mulotte wrote me privately: > I presume you mean I should use - suest - on each sample and then - test - on age2, right ? Remember that the Statalist FAQ asks you not continue a discussion outside the statalist. If you find my answer unclear, than chances are that others following this discussion would feel the same way and would thus also benefit from further clarification. To answer your question, no, I mean you use the model with interaction terms just as I advised you in my earlier post <http://www.stata.com/statalist/archive/2011-07/msg00074.html>. So, to continue that example: *-------------------------- begin example -------------------- use http://www.stata-press.com/data/r11/nlswork, clear // estimate the model reg ln_wage i.south i.south#(c.age##c.age c.grade c.birth_yr) // see how the coefficients are called reg, coeflegend // test whether both curves are equally peaked // (that hypothesis is in this case rejected) test _b[0b.south#c.age#c.age] = _b[1.south#c.age#c.age] *-------------------- end example ------------------------- (For more on examples I sent to the Statalist see: http://www.maartenbuis.nl/example_faq ) Both -sureg- and the model with interaction terms have their advantages and disadvantages, but I would stick to one of these models and not test whether the turning points are equal within the model with interactions and test whether the curves are equally steep within the -sureg- model. Hope this helps, Maarten -------------------------- Maarten L. Buis Institut fuer Soziologie Universitaet Tuebingen Wilhelmstrasse 36 72074 Tuebingen Germany http://www.maartenbuis.nl -------------------------- * * 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/