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From |
Steven Frenk <smf7@duke.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: Logistic Regression Coefficients Using MIM and SVY |

Date |
Wed, 31 Mar 2010 11:25:00 -0400 |

I am estimating logistic regression models using STATA/SE 10.1 (Windows) and the MIM and SVY commands. The models include my dependent variable and one of my independent variables [mim: svy: logit DV IV, or]. In four of my models, I get weird parameter estimates?the odds ratio and CI?s are whole numbers and the standard error is zero. For example: . mim: svy: logit z_tot_alldisorders z_totprogs06, or Multiple-imputation estimates (svy: logit) Imputations = 5 Survey: Logistic regression Minimum obs = 1499 Minimum dof = 1000.0 ------------------------------------------------------------------------------ z_tot_alld~s | Odds Rat. Std. Err. t P>|t| [95% Conf. Int.] FMI -------------+---------------------------------------------------------------- z_totprogs06 | 1 0 7.53 0.000 1 2 . ------------------------------------------------------------------------------ The problem does not exist when I just use the SVY command: . svy: logit z_tot_alldisorders z_totprogs06, or (running logit on estimation sample) Survey: Logistic regression Number of strata = 1 Number of obs = 7495 Number of PSUs = 7495 Population size = 7485.1806 Design df = 7494 F( 1, 7494) = 283.75 Prob > F = 0.0000 ------------------------------------------------------------------------------ | Linearized z_tot_alld~s | Odds Ratio Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- z_totprogs06 | 1.469695 .0335955 16.84 0.000 1.405292 1.53705 ------------------------------------------------------------------------------ This is only occurring with four of my thirteen independent variables. Here?s some information about the four variables with the strange estimates: --Two of them are continuous variables and two are dummy variables. --Three had missing values (imputed with ice), and one did not have any missing values. --When I run logistic models with each imputed data set and use the svy: logit command, the parameter estimates produced are logical and valid (so I don't think it is an imputation problem). I've tried looking on google and statalist for information regarding this problem, but I have not found any answers. Does anyone know why this is occurring and how to fix it? Thank you for your time. ************************ Steven M. Frenk PhD Candidate Department of Sociology Duke University steven.frenk@duke.edu (919) 672-7495 * * 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/

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