Table 1 Participants’ characteristics by sex^a

School grade

 Secondary 1

24.71

23.23

23.98

0.043

 Secondary 2

24.71

24.25

24.51

 Secondary 3

26.49

26.00

26.31

 Secondary 4

24.08

26.52

25.20

Father’s education level

 Junior secondary school or below

26.51

29.50

27.83

<0.001

 Senior secondary school or matriculation

37.34

39.04

38.22

 University or college or above

18.25

14.70

16.57

 Missing

17.90

16.77

17.38

Mother’s education level

 Junior secondary school or below

27.12

30.48

28.66

<0.001

 Senior secondary school or matriculation

40.34

43.06

41.67

 University or college or above

15.27

11.03

13.25

 Missing

17.27

15.42

16.42

Living arrangement with parents

 Living with both parents

82.83

82.50

82.70

0.143

 Living with the mother only

9.25

9.92

9.55

 Living with the father only

3.14

2.82

2.99

 Living with none of the parents

2.67

3.34

2.97

 Missing

2.11

1.39

1.79

Father’s age (mean ± SD)

46.95 ± 6.78

47.08 ± 6.59

47.02 ± 6.68

0.428

Whether born in HK/length of residency

 Yes, born in HK

79.89

77.05

78.58

<0.001

 No, stayed in HK ≥7 years

11.81

13.33

12.53

 No, stayed in HK <7 years

5.55

7.48

6.43

 No, can’t remember when came to HK

2.00

1.66

1.84

 Missing

0.75

0.48

0.62

HBM constructs

 Perceived Susceptibility to IA

2.36 ± 1.08

2.35 ± 1.00

2.36 ± 1.04

0.558

 Perceived Severity of IA

3.29 ± 1.26

3.52 ± 1.12

3.40 ± 1.20

<0.001

 Perceived Barriers (reducing use)

10.39 ± 3.99

10.81 ± 3.82

10.59 ± 3.92

<0.001

 Perceived Social Benefits (Internet use)

13.70 ± 4.20

13.40 ± 3.99

13.57 ± 4.11

<0.001

 Cue to Action Scale (reducing use)

5.46 ± 2.05

4.91 ± 1.95

5.21 ± 2.03

<0.001

 Perceived Self-efficacy (reducing use)

7.08 ± 2.04

7.30 ± 1.90

7.18 ± 1.98

<0.001

Perceived number of peers with IA (PNPIA)

 Nil

16.69

18.08

17.35

<0.001

 Only a few

41.21

52.30

46.34

 Quite a number

29.26

24.57

27.10

 A large number

12.84

5.05

9.21