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Table 3 Self-perceived oral health regression results

From: Socioeconomic inequalities in self-perceived oral health among adults in Chile

  OLS Heckman Two-step Ordered Model Ordered Model Sample Selection
Coef. p-value Coef. p-value Coef. p-value Coef. p-value
Sex −3.991 0.000 −2.433 0.042 −0.351 0.000 −0.092 0.411
Age (base: 18–30)
 31–40 3.912 0.001 2.807 0.029 0.338 0.000 0.144 0.197
 41–50 5.970 0.000 4.622 0.001 0.515 0.000 0.265 0.032
 51–61 7.219 0.000 6.429 0.000 0.637 0.000 0.447 0.000
Head of household 1.522 0.038 −1.506 0.456 0.161 0.008 −0.270 0.049
Married/partner −0.364 0.609 −0.186 0.784 −0.030 0.636 −0.002 0.973
Children under 5 2.273 0.001 2.974 0.000 0.196 0.001 0.265 0.000
Children aged 5-18 0.253 0.327 0.498 0.161 0.016 0.497 0.047 0.053
Education (base: Middle or less)
 Incomplete secondary school −1.184 0.217 −2.162 0.069 −0.113 0.182 −0.231 0.004
 Complete secondary school −3.455 0.001 −4.749 0.000 −0.320 0.001 −0.450 0.000
 Higher Education −6.031 0.000 −7.206 0.000 −0.536 0.000 −0.623 0.000
Employed full time 0.211 0.739 1.420 0.196 0.004 0.941 0.170 0.018
Employed part time −1.018 0.251 −1.425 0.124 −0.116 0.130 −0.154 0.048
Healthcare system (base: Public Insurance A, most vulnerable)
 Public Insurance B −2.493 0.002 −3.166 0.001 −0.231 0.000 −0.291 0.000
 Public Insurance C −2.164 0.039 −3.640 0.004 −0.209 0.021 −0.379 0.000
 Public Insurance D (least vulnerable) −2.382 0.006 −3.475 0.007 −0.223 0.003 −0.341 0.000
 Public Insurance unknown category −2.131 0.172 3.431 0.771 −0.262 0.053 0.518 0.204
Inverse Mills ratio (IMR)    −4.294 0.105     
Constant 32.623 0.000 42.148 0.000     
Observations 1,394   1,394   1,394   1,394  
R-squared 0.138        
LR test indep equations        6.04 0.014
  1. Abbreviations: OLS Ordinary Least Squares, Coef estimated coefficient
  2. The dependent variable is the OHIP-14 score. Independent variables are described in Table 1. The first two columns report OLS estimates without correction for sample selection. The next two correct for sample selection using Heckman’s two-step estimator. The third set estimates an ordered multinomial model, whereas the final set corrects the ordered multinomial model for sample selection. Clustered standard errors at the municipality of residence level are reported
  3. Inv. Mills ratio (IMR) is the sample selection correction variable in the Heckman model. After estimating the participation equation (Additional file 1: Table S1), for each observation in the sample we compute \( \hat{\lambda} \) =ϕ(x3 \( \widehat{\beta_3} \))/Φ(x3 \( \widehat{\beta_3} \)), where ϕ is the density of the Normal Distribution and Φ is its cumulative
  4. LR test indep equations (likelihood-ratio test) tests hypothesis that the errors of OHIP-14 and participation equations are uncorrelated in the ordered response model