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| From | Maarten Buis <maartenlbuis@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: xttobit & stata 12: Initial values not feasible |
| Date | Tue, 3 Jul 2012 15:57:30 +0200 |
On Tue, Jul 3, 2012 at 3:39 PM, Surender Komera wrote: > I have not centered explanatory variables (x variables). How can i do > that? It will be really helpful if you can explain. Say you have year of birth, than you would not want to enter it as is in a random effects model. A lot of the (random) action in random effects models is in the constant, and if you entered year of birth as is than that would (typically) be a huge extrapolation, i.e. it would refer to people born in the year 0. Say you want to center at 1950, than you just create a new variable which contained the year of birth - 1950. You can pick any number that is meaningful as long as it is within (or close to) the range of your data. This is something you only want to do to your continuous explanatory variables, not your dependent variable an not to any of the indicator (dummy) variables. -- 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/