Table 1 Questionnaire items and response categories of individual and family environmental variables

 Child perception of the screen time recommendations (CQ)

Children my age should not watch TV/DVD or use a computer/game console for leisure activities for more than… (ICC = 0.51/0.58)

1 = 30 min/day; 2 = 1 h/day; 3 = 2 h/day; 4 = 3 h/day; 5 = 4 h/day

 Child attitude^a (CQ)

I think watching TV/DVD or using the computer/game console for leisure activities is good for me (ICC = 0.59/0.59)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Child preference^a (CQ)

I like watching TV/DVD or using a computer/game console for leisure activities (ICC = 0.56/0.51)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Child self-efficacy (CQ)

I find it hard to NOT watch TV/DVD or use a computer/game console for leisure activities (ICC = 0.57/0.69)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Child habit^a (CQ)

Watching TV/DVD or using a computer/game console for leisure activities is something that I do without really thinking about it (ICC = 0.60/0.63)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Child agreement with rules^a (CQ)

It is OK for me that my parents have rules about how much I can watch TV/DVD or use a computer/game console for leisure activities (ICC = 0.53/0.59)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Parental behaviour^a (CQ)

How often do your parents/guardians watch TV/DVD or use a computer/game console for leisure activities? (ICC = 0.73/0.46)

1 = Always; 2 = Often; 3 = Sometimes; 4 = Not often; 5 = Never

 Parental co-participation (CQ)

How often do you watch TV/DVD or use a computer/game console for leisure activities with your parents/guardians? (ICC = 0.65/0.56)

1 = Never; 2 = Less than once a week; 3 = Once a week; 4 = 2–4 days a week; 5 = 5–6 days a week; 6 = Every day, once a day; 7 = Every day, more than once a day

 Parental subjective norm (CQ)

If I watch TV/DVD or use a computer/game console for leisure activities, my parents/guardians think this is good for me (ICC = 0.57/0.52)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Parental perception of the screen time recommendations (PQ)

Children of same age as my child should not watch TV/DVD or use a computer/game console for leisure activities for more than… (ICC = 0.67/0.68)

1 = 30 min/day; 2 = 1 h/day; 3 = 2 h/day; 4 = 3 h/day; 5 = 4 h/day

 Parental avoidance of negative modeling behaviour^a (PQ)

If I would like to watch TV/DVD or use a computer/game console for leisure activities, I would refrain from doing so if my child were there (ICC = 0.62/0.47)

1 = Always; 2 = Often; 3 = Sometimes; 4 = Not often; 5 = Never

 Parental strictness item 1 (CQ)

My parents/guardians let me watch TV/DVD or use a computer/game console whenever I want (ICC = 0.73/0.67)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Parental strictness item 2 (CQ)

If I ask my parents/guardians to watch TV/DVD or use a computer/game console for leisure activities, I can do so (ICC = 0.49/0.65)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Parental rules (CQ)

My parents/guardians have rules about how much I am allowed to watch TV/DVD or use a computer/game console for leisure activities (ICC = 0.56/0.69)

1 = I fully agree; 2 = I partly agree; 3 = Neither agree nor disagree; 4 = I partly disagree; 5 = I fully disagree

 Child participation in setting rules (CQ)

Did you take part in setting these rules for TV/DVD watching or using a computer/game console for leisure activities (ICC = 0.68/0.68)

0 = No; 1 = Yes

 Parental monitoring^a (PQ)

I pay attention to the amount of time my child watches TV/DVD or uses a computer/game console for leisure activities (ICC = 0.67/0.74)

1 = Always; 2 = Often; 3 = Sometimes; 4 = Not often; 5 = Never

 Parental negotiation^a (PQ)

I discuss the amount of time my child is allowed to watch TV/DVD or to use a computer/game console for leisure activities with him/her (ICC = 0.71/0.71)

1 = Always; 2 = Often; 3 = Sometimes; 4 = Not often; 5 = Never

 Parental education (PQ)

What is the highest level of education you have completed?

1 = Elementary school; 2 = Secondary school; 3 = College/University (Bachelor degree or equivalent); 4 = College/University (Master degree; equivalent or more)

Response category 1 and 2 were combined into 1 = Low education; Response category 3 and 4 were combined into 2 = High education

 Number of TV’s in the household (CQ)

How many TV’s are there in your home? (ICC = 0.87)

1 = None; 2 = 1; 3 = 2; 4 = 3; 5 = 4; 6 = More than 4

 Having a TV in the bedroom (CQ)

Do you have a TV in your own bedroom? (ICC = 0.87)

0 = No; 1 = Yes

 Having a TV in the kitchen (PQ)

Do you have a TV in your kitchen? (ICC = 0.88)

0 = No; 1 = Yes

 Number of computers in the household (CQ)

How many computers are there in your home? (Include laptops and iPads) (ICC = 0.92)

1 = None; 2 = 1; 3 = 2; 4 = 3; 5 = 4; 6 = More than 4

 Having an own computer (CQ)

Do you have your own computer? (ICC = 0.96)

0 = No; 1 = Yes

 Number of consoles in the household (CQ)

How many game consoles (e.g. Playstation, Xbox, Nintendo (Wii, GameCube, DS)) are there in your home? (ICC = 0.80)

1 = None; 2 = 1; 3 = 2; 4 = 3; 5 = 4; 6 = More than 4

 Having an own console (CQ)

Do you have your own game console (e.g. Playstation, Xbox, Nintendo (Wii, GameCube, DS))? (ICC = 0.88)

0 = No; 1 = Yes