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st: Logistic Regression Coefficients Using MIM and SVY
From
Steven Frenk <[email protected]>
To
[email protected]
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
[email protected]
(919) 672-7495
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