STAT Online homework help Worksheet Difficulty: 1Easy Learning Objective: 0806 Know when to use Students t instead of z to estimate μ. The Environmental Protection Agency (EPA) requires that cities monitor over 80 contaminants in their drinking water. Samples from the Lake Huron Water Treatment Plant gave the results shown here. Only the range is reported, not the mean (presumably the mean would be the midrange). Substance MCLG Range Detected Allowable MCLG Origin of Substance Chromium 0.40 to 0.61 100 Discharge from steel and pulpmills, natural erosion Barium 0.004 to 0.015 2 Discharge from drilling wastes,metal refineries, natural erosion Fluoride 1.06 to 1.15 4 Natural erosion, water additive, discharge from fertilizer and aluminum factories MCLG = Maximum contaminant level goal For each substance, estimate the standard deviation σ by assuming Uniform Distribution and Normal Distribution shown in Table 8.11 in Section 8.8. (Round your answers to 4 decimal places.) Uniform Distribution Normal Distribution Chromium Barium