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Table 1 Demographic characteristics of participating and non-participating families

From: Efficacy of the Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline in Twin Families (VIPP-Twins): Study protocol for a randomized controlled trial

  Participating families (n = 225) Non-participating, eligible families (n = 131)  
Twin characteristics
 Age at recruitment M (SD) 3.60 (0.58) 3.56 (0.53) p = .45
 Gender (% boys) 49.8 55.0 p = .35
 Country of birth (% Netherlands) 99.6 100.0 p = .45
Family characteristics
 Primary parent (%)1    p = .97
  Biological mother 92.0 86.4  
  Biological father 8.0 7.6  
 Age primary parent M (SD) 36.81 (4.58) 37.29 (4.51) p = .39
 Age second parent M (SD) 38.45 (5.65) 39.52 (4.78) p = .11
 Country of birth (% Netherlands)
  Primary parent 95.1 92.8 p = .39
  Second parent 96.0 92.8 p = .21
 SES – based on parents educational level (%)    p = .18
  Low 7.1 6.1  
  Medium 39.6 49.6  
  High 53.3  44.3  
 Number of children in the family M (SD) 2.82 (0.78) 2.90 (1.00) p = .41
 Primary parents’ marital status (%)    p = .25
  Married or registered partnership 69.2 78.6  
  Cohabiting 26.8 16.8  
  Single parent 3.6 4.6  
 Family type (%)    p = .28
  Biological parent(s) 98.2 96.1  
  Adoptive parent 0.9 0.8  
  Step parent 0.9 1.6  
  Other 0.0 1.6  
  1. 1The percentages for the non-participating group do not sum to 100 %, because parents in seven families spend an equal amount of time with their children. The p-value is based on the values shown in the table