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Table 3 Multilevel model for item non-response in SAQ (n = 21,763)

From: Mixing mixed-mode designs in a national health interview survey: a pilot study to assess the impact on the self-administered questionnaire non-response

 Model 1 (Empty model)Model 2Model 3a
OR (95% CI)OR (95% CI)OR (95% CI)
Fixed effects at item level
 Mode: P&P 2.25 (1.44–3.52) *2.13 (1.33–3.43) *
Fixed effects at respondent level
 Age  1.00 (0.98–1.02)
 Men  0.81 (0.52–1.28)
 Higher education level b  0.79 (0.47–1.33)
 Country of birth: non-Belgium  1.00 (0.55–1.81)
 Employment status (ref: non-employed) c
 employed  0.91 (0.48–1.71)
 student  0.84 (0.31–2.26)
 Household size: 1+  0.97 (0.59–1.58)
Random parameters
 Variance between respondents (SE)1.92 (0.28) *1.70 (0.25) *1.66 (0.25) *
 ICC respondents0.370.340.34
 PCV 11.4%13.6%
 Model fit: −2 Log Likelihood7840.897829.08 **7826.66
  1. Values based on SAS Proc Glimmix; Estimation method = Laplace
  2. *p value < 0.05; ** = likelihood ratio test significant; ICC = intra-class coefficient of correlation; PCV = proportional change in variance; SAQ = self-administered; P&P = paper-and-pencil
  3. The PCV expresses the change in the respondents’ level variance between the initial model and the model with more terms.
  4. a Best fitting model
  5. b For students the education level equals the highest education level in the household. If this was not possible it was based on their current field of study
  6. c “Employed” refers to respondents who had a paid job for at least one hour a week at the moment of the interview, “Unemployed” refers to respondents without a paid job at the moment of the interview, “Student” refers to respondents who were (fulltime or part-time) enrolled in the regular education system at the moment of the interview. Students who had a (part-time) paid job were classified as students