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| From | "Li, Rui (CDC/ONDIEH/NCCDPHP)" <eok8@cdc.gov> |
| To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
| Subject | st: how to us prais in a situation with comparison group |
| Date | Wed, 2 May 2012 15:44:22 +0000 |
I am doing a segmented linear regression, the model is Yt=β0 + β1*group + β2timet + β3*policy1t + β4 *policy2t + β5*time after policy2t + β6*group* timet + β7*group* policy1t + β8*group* policy2t + β9*group* time after policy2t + et I want to use prais to take into account of the autocorrelation, however, when I use tsset time, the program gave me error message "repeated time values in sample". It is because I have a comparison group and it has the same time variable as the treatment group. What should I do in this case? Also, if I use tsset time, should time still be a variable in the model or should it be left out of the model? Thanks! Rui * * 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/