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. Author manuscript; available in PMC: 2011 Nov 28.
Published in final edited form as: Addiction. 2009 Jul 14;104(11):1874–1880. doi: 10.1111/j.1360-0443.2009.02678.x

Table 1.

Statistical tests of association between Rural Urban Commuting Area codes and Distribution of Drug Index Loads for 96 Oregon municipal wastewater treatment plants.

Equivalency across RUCA* Trend across RUCA**
Substance df chi-square p-value df chi-square p-value
Benzoylecgonine (cocaine metabolite) 8 26.1 0.001 2 10.97 0.004
Methamphetamine 4 3.51 0.477 2 0.894 0.640
MDMA 8 8.88 0.353 2 6.16 0.046
*

Pearson’s chi-square statistic

**

Partition of Pearson’s chi-square statistic for ordered categorical variables