D The following maps depict the concentration of two narcotics recovered from several municipal wastewater systems across Oregon state in 2008 (left map: methamphetamine; right map: a metabolite produced by the body from cocaine). The size of each circle represents the concentration of the narcotic recovered from each municipal wastewater system, separated into four levels: . Large circles represent wastewater systems whose narcotic concentrations fall within the upper tertile (upper 33.33%) of narcotic concentrations observed out of all observed systems. . The medium circles represent wastewater systems whose narcotic concentrations fall within the middle tertile (middle 33.33%) of all observed systems. . Small circles represent wastewater systems whose narcotic concentrations fall within the lower tertile (lower 33.33%) of all observed systems. . Small black dots and x's represent wastewater systems that show traces of narcotics at such low concentrations that is impossible to quantify them. Methamphetamine Benzoylecgonine (Cocaine metabolite) O O Oo Drug Load X Not detected Drug Load Below quantification Lowest Tertile O Lowest Tertile Middle Tertile Middle Tertile Upper Tertile TO Upper Tertile RUCA Category Oo RUCA Category Urban Large Rural City/Town Large Rural City/Town 100 Miles Small Rural Town 100 Mile Small Rural Town Figure 1. Drugs detected in Oregon municipal wastewater from a single day's sample in 2008 Use this information to answer the next three questions.D Question 2 1 pts What kind of variable is reflected by the methamphetamine variable represented in the map on the left? Select all that apply. O nominal variable index O numerical variable O discrete variable O continuous variable O categorical variable indicator variable O ordinal variable O multilevel variable