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From | Sirak <sirak22@googlemail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: bootstrap _b VS bootstrap _se |
Date | Wed, 21 Jul 2010 09:25:18 +0200 |
Thanks Marteen for your valuable comment as usual. But one think I didnt get it here is, the coefficients for sureg and bootstrap _b, reps(1000) : sureg are the same. the change is only in standard deviation and confidence interval. I was expecting to see a little change in the coeeficients, but none of them changed. I have read this suggested that the original findings were replicated. Is that right? Thanks for the help. best regards, Sirak On Tue, Jul 20, 2010 at 10:52 AM, Maarten buis <maartenbuis@yahoo.co.uk> wrote: > --- On Tue, 20/7/10, Sirak wrote: >> I have run bootsraping for coefficient and standard >> deviation with some constraints as in the following: >> >> constraint 1 _b[y3x1] = 1 - _b[y2:x1] - _b[y1:x1]/// >> constraint 2 _b[y3x2] = 1 - _b[y2:x2] - _b[y1:x2]/// >> constraint 3 _b[y3x3] = 1 - _b[y2:x3] - _b[y1:x3]/// >> >> 1) bootstrap _b, >> reps(100) : sureg (y1 x1 x2 x3 x4) (y2 x1 x2 >> ) (y3 x1 x2 x4 ), constraints (1 2 3) >> /// >> 2) bootstrap _se, >> reps(100) : sureg (y1 x1 x2 x3 x4) (y2 x1 x2 >> ) (y3 x1 x2 x4 ), constraints (1 2 3) /// >> >> In the first equation the constraint works properly and I >> found the sum of respective X's in each equation is one. >> However, in the second equation, i got the estimates..... >> no errors are observed..., but the constraint that the sum >> of each respective x equals to one fails. > > In the second command you are bootstrapping the standard > errors, i.e. you are looking how uncertain your estimate > of uncertainty is. That is didactically not a bad idea, it > clearly illustrates that we should not take our p-value of > 5% to strictly as there is uncertainty in that p-value as > well. However, I doubt whether that is what you want to do > here. > > Anyhow, the constraint you specified says that your > parameters add up to one, not that your standard errors add > up to one. So Stata does exactly what you told it to do. > > 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/ > * * 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/