TABLE 1

Dropping Out of the Study in Relation to Baseline Characteristics

CharacteristicStayed InDropped OutOdds Ratio or DifferenceP
Gender, n (%)
    Male1129 (50.1)118 (48.4)Reference
    Female1126 (49.9)126 (51.6)1.03 (0.86–1.24)a.72
Race, n (%)
    White1712 (75.9)169 (69.3)Reference
    Other543 (24.1)75 (30.7)1.28 (1.00–1.63)a.048
Age, n (%)
    9 y452 (20.0)44 (18.0)0.90 (0.66–1.23)a.50
    10 y865 (38.4)91 (37.3)0.97 (0.78–1.21)a.80
    11 y716 (31.8)79 (32.4)1.02 (0.81–1.29)a.87
    12 y222 (9.8)30 (12.3)1.25 (0.85–1.83)a.25
School performance, n (%)
    Excellent924 (41.2)62 (25.4)0.62 (0.48–0.80)a<.001
    Good957 (42.6)129 (52.9)1.24 (1.03–1.49)a.022
    Average/below average363 (16.2)53 (21.7)1.34 (1.01–1.79)a.045
Friend smokes, n (%)
    No2091 (92.7)228 (93.4)Reference
    Yes164 (7.3)16 (6.6)0.90 (0.54–1.51)a.69
Either parent smokes, n (%)
    No1508 (68.2)111 (50.2)Reference
    Yes703 (31.8)110 (49.8)1.57 (1.28–1.91)a<.001
Parent education, n (%)
    High school diploma or less670 (30.4)112 (50.9)1.67 (1.37–2.04)a<.001
    Some college846 (38.4)87 (39.5)1.03 (0.83–1.28)a.79
    Bachelor's degree or more687 (31.2)21 (9.5)0.31 (0.20–0.47)a<.001
Summary score, mean ± SDb
    Movie smoking exposure40.74 ± 41.0846.78 ± 47.226.05 (0.54–11.56)c.03
    Sensation-seeking4.70 ± 2.964.85 ± 3.050.15 (−0.24 to 0.54)c.45
    Rebelliousness2.32 ± 2.702.75 ± 3.070.43 (0.07–0.79)c.02
    Self-regulation8.53 ± 2.288.55 ± 2.420.02 (−0.28 to 0.32)c.90
    Self-esteem8.94 ± 2.708.97 ± 2.700.02 (−0.33 to 0.38)c.90
    Maternal responsiveness11.91 ± 3.3611.73 ± 3.67−0.18 (−0.63 to 0.27)c.44
    Maternal monitoring20.82 ± 4.3520.56 ± 4.70−0.26 (−0.84 to 0.32)c.38
  • a Unadjusted odds ratio and 95% CI.

  • b A higher value indicates more of the characteristic. The scales for self-esteem, self-regulation, and sensation-seeking were 0 to 12. Rebelliousness was scaled 0 to 18, maternal responsiveness was scaled 0 to 15, and maternal monitoring was scaled 0 to 27.

  • c Mean differences and 95% CI.