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. Author manuscript; available in PMC: 2012 Feb 1.
Published in final edited form as: Biol Psychiatry. 2010 Oct 20;69(3):260–265. doi: 10.1016/j.biopsych.2010.08.017

Table 1.

Participant Characteristics

Control
(N=13)		 Active
(N=14)		 Test statistic
and p-value
Years of education [Mean (SD)] 12.0 (1.7) 12.4 (1.7) t25 = 0.64; p = 0.528
Quick Test IQ [Mean (SD)] 37.1 (5.1) 37.4 (3.0) t25 = 0.17; p = 0.862
Years using Stimulants [Median (IQR)]* 14.5 (11.5, 20.5) 12 (3, 13) χ2 (1} = 3.24; p = 0.085
Primary Stimulant of Abuse [%] **
   Cocaine only 77 71
   Methamphetamine only 15 22 χ2 (2} = 0.16; p = 0.922
   Both cocaine and methamphetamine 8 7
Has history of non-stimulant use [%] 77 79 χ2 (1} = 0.01; p = 0.918
*

Failed to collect data for two participants, one from each group.

**

A chi-square test of independence with degrees of freedom (df)=2