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. Author manuscript; available in PMC: 2015 Mar 1.
Published in final edited form as: J Res Adolesc. 2013 Feb 25;24(1):117–130. doi: 10.1111/jora.12030

Table 3.

Use and Quantity of Use From Grade 9 to Grade 12

First recorded
usea
 Any recorded
use
 Average quantity useb
N Grade % N Count % N Count M SD P
201 9 5% 11 17% 34 52.74 143.03 0.159
199 10 6% 12 20% 39 171.40 452.49 0.212
202 11 8% 17 28% 57 176.06 476.78 0.108
201 12 10% 21 35% 70 150.88 530.81 0.440
a

A total of 20.32% of the sample reported first use before high school.

b

Quantity of use in grams.

c

Quantity of use is log transformed to minimize skew.