Table 3 Differences between students who were retained beyond baseline (repeat) and those that were lost to follow-up (single) on baseline scores

Cannabis Knowledge

8.58

8.78

1

1727

1.46

p = 0.23

Psychostimulant Knowledge

8.26

8.51

1

1721

2.16

p = 0.14

Cannabis Attitudes

9.64

8.24

1

1730

47.24

p < 0.0001

Psychostimulant Attitudes

10.20

8.91

1

1730

41.57

p < 0.0001

Cannabis frequency of use (three months)

0.47

0.12

1

1720

48.25

p < 0.001

Meth/amphetamine frequency of use (12 months)

0.22

0.07

1

1727

17.61

p < 0.001

Ecstasy frequency of use (last 12 months)

0.29

0.09

1

1727

29.8

p < 0.001

Cannabis intention 12 months

1.10

0.60

1

1729

44.61

p < 0.001

Meth/amphetamine intention 12 months

0.62

0.30

1

1727

38.20

p < 0.001

Ecstasy intention 12 months

0.71

0.38

1

1727

29.66

p < 0.001

Single

Repeat

df

χ ²

p

Lifetime cannabis use

0.22

0.10

1

33.58

p < 0.0001

Lifetime Methamphetamine use

0.10

0.03

1

27.37

p < 0.0001

Lifetime ecstasy use

0.12

0.05

1

32.2

p < 0.0001