Table 1

Description of the sample and crude associations with smoking

Continuous variables	Median	IQR^*	Association with smoking^†
Continuous variables	Median	IQR^*	Crude	p Value
Categorical variables	n	%	OR	p Value
Smoking status
Never smoked in last year	1406	71.1
Ever smoked in last year	572	28.9
Missing	21
Film-smoking exposure
Beach method (does not consider times seen)	96	60–134	2.08	0.001
Modified Beach method (considers times seen)	196	120–314	2.59	<0.0001
Media use/access
Number of hours watching TV/DVDs on weekdays
Quartile 1 (0–2 h)	610	30.5	Ref
Quartile 2 (3 h)	321	16.1	1.07	0.67
Quartile 3 (4–5 h)	389	19.5	1.31	0.09
Quartile 4 (6 or more hours)	460	23.0	1.32	0.62
Missing	219	11.0	1.14	0.49
Has DVD or video player in bedroom
Yes	1798	89.9	Ref
No	155	7.8	0.75	0.46
Missing	46	2.3
Has access to the internet/web in bedroom
Yes	1061	53.1
No	787	39.4	0.64	0.06
Missing	151	7.6
Has digital, satellite or cable TV channels
Yes	1307	65.4
No	599	30	1.02	0.86
Missing	93	4.7
Rules about media
Television/films rules
Parental approval of what is watched:
Definitely not/possibly not	285	14.5	Ref
Don't know	345	17.6	1.17	0.29
They wouldn't mind	944	48	1.06	0.75
They would approve	391	19.9	1.09	0.66
Missing	34
Allowed to watch 18 certificate films
Yes	1852	92.6	Ref
No	147	7.4	0.19	<0.0001
Has to finish homework/chores before watching TV
No	1655	82.8	Ref
Yes	344	17.2	0.4	<0.0001
Only allowed to watch a certain amount of TV
No	1915	95.8	Ref
Yes	84	4.2	0.37	0.006
Access to some TV programs restricted
No	1523	92.5	Ref
Yes	123	7.5	0.17	<0.0001
Allowed to watch anything on TV
Yes	1586	79.3	Ref
No	413	20.7	0.20	<0.0001
Breaks TV/DVD rules:
Assume don't have rules about watching TV	905	47.9	Ref
Yes, I often break them	163	8.6	1.13	0.51
Yes, I sometimes break them	443	23.5	0.3	<0.0001
No, I follow these rules	377	20	0.39	<0.0001
Missing	111
TV/films parenting scale from above six variables (α=0.68) (0–6) each one point increase is adding an item	1	0–3	0.71	<0.0001
Film viewing pattern
Views films with parents (0–4)	2	1–3		0.43
Internet rules
Internet access restricted or not
Yes	327	16.5	Ref
No	1317	66.4	0.79	0.125
Don't know	339	17.1
Missing	16
Internet usage supervised?
No	1431	0.72	Ref
Yes	216	0.11	0.67	0.025
Missing	352	0.21
Family background
Housing tenure
Owner-occupied	1453	20.8	Ref
All other types of accommodation	416	72.7	1.46	0.005
Missing	130	6.5
Parental education:
Either/only parent remained at school beyond age 16	961	48.1	Ref
Both/only parent(s) left school at 16 years of age	671	33.6	1.52	0.001
Missing	367	18.4
Family connectedness: (0–8)	6	5–7	0.35	<0.0001
Parental monitoring: (0–8)	6	4–7	0.46	<0.0001
Individual characteristics
Gender
Male	1008	50.6	Ref
Female	984	49.4	1.82	<0.0001
Missing	7
Number of national school examinations being sat
7+	1008	50.4	Ref
6 or less	802	40.1	1.78	<0.0001
Missing	189	9.5	2.31	<0.0001
School leaving plans
Plans to remain in school beyond statutory leaving age	1350	69.3	Ref
Plans to leave school as soon as legally entitled to	363	18.7	3.59	<0.0001
Don't know	233	12	1.28	0.17
Missing	53
Peer behaviours
Peer smoking (0 none, 4 most/all)	1	2–2	51.7	<0.0001
Views movies with friends	2	1–2	3.85	<0.0001

* Medians and IQR reported for variables in their original form.
† For this assessment, all ordinal and continuous variables scaled so zero represents lowest risk category and one represents the highest response category.