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Table 1 The frequency distribution of background variables

From: Longitudinal measurement invariance and explanatory IRT models for adolescents’ oral health-related quality of life

Factors

Baseline (n = 649)

Followed- up (n = 415)

  

n

%

n

%

Gendera

Boys

319

49.2

Girls

330

50.8

Father’s education levela

College graduate or above

81

12.5

Senior secondary school (S4‑7)

313

48.2

Junior Secondary school (S1‑3)

167

25.7

Mother’s education levela

Below Secondary school

88

13.6

College graduate or above

110

16.9

Senior secondary school (S4‑7)

267

41.1

Junior Secondary school (S1‑3)

184

28.4

Below Secondary school

88

13.6

Student Dental Care Service/ Dental insurancea

Yes

636

98.0

No

13

2.0

Monthly family income

>$40,000

96

14.8

81

19.5

$30,000‑$40,000

65

10.0

42

10.1

$20,000‑$30,000

101

15.6

69

16.6

$10,000‑$20,000

226

34.8

165

39.8

<$10,000

161

24.8

58

14.0

Snacking frequency between meals

3 times or more

54

8.3

38

9.2

Twice

123

19.0

81

19.5

Once

334

51.4

202

48.7

None

138

21.3

94

22.7

Daily brushing frequency

Twice or more

467

72.0

303

73.0

Less than twice

182

28.0

112

27.0

Both parents employed

Yes

417

64.3

276

66.5

No

232

35.7

139

33.5

Maximum CPI

Healthy gum/ No bleeding or calculus

89

13.7

44

10.6

Bleeding on probing

139

21.4

46

11.1

Calculus deposits

421

64.9

325

78.3

DMFT

0

446

68.7

193

46.5

1

109

16.8

67

16.1

2

52

8.0

47

11.3

> 3

42

6.5

108

26.1

Mean (s.d.)

0.55

(1.01)

1.70

(2.34)

  1. aOnly collected in the baseline study