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From |
peselb@pwi.unizh.ch |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: crossed random coefficients using GLLAMM |

Date |
Fri, 7 Oct 2005 15:45:54 +0200 |

Dear all I have data on dichotomous vote choices (i) nested within voters (j) nested within referendums (k). Referendums comprise 1-6 propositions (that’s why I potentially have multiple observations per voter). I have set up a GLLAMM-model with random intercepts at the level of voters, propositions and referendums, i.e. a cross-classified model where the cross-classification (voters/propositions) is still nested within the higher level of referendums. Unfortunately, Stata gives various error messages (conformability error, likelihood cannot be computed etc.), and I have no idea whether they relate to model specification and/or to computational difficulties. Therefore, I would very much appreciate any comments on model specification: /* generate intercepts for level j and k */ gen byte cons1=1 gen byte cons2=1 eq c1: cons1 eq c2: cons2 /* generate random effects for propositions 1,2,..,max per referendum to let them randomly vary at level k */ eq p1: prop1 eq p2: prop2 eq p3: prop3 eq p4: prop4 eq p5: prop5 eq p6: prop6 /* constrain them to have equal variances =one random intercept at proposition level!), i.e. to hold the diagonal elements of the Cholesky decomposition matrix equal; off-diagonal elements are constraint to 0 by nocorrel option in GLLAMM (see below) */ constraint define 1 prop1=prop2 constraint define 2 prop2=prop3 constraint define 3 prop3=prop4 constraint define 4 prop4=prop5 constraint define 5 prop5=prop6 /* and this is the (empty) model.. */ gllamm choice, i(voter ref) link(probit) fam(bin) nrf(1,7) eqs(c1 c2 pro1 pro2 pro3 pro4 pro5 pro6) nocorrel constraints(1 2 3 4 5) nip(3) trace In particular, I have some doubts whether to include c1, the random intercept at the referendum level? Does anyone have some suggestions on model specification? Thanks a lot for taking the trouble to help me! Best, Peter ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program. * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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