The Environmental Protection Agency (EPA) requires that cities monitor over 80 c

Question

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 Chromium Barium MCLG Range Detected 0.48 to 0.67 0.004 to 0.017 Allowable MCLG 100 Origin of Substance Discharge from steel and pulp mills, natural erosion Discharge from drilling wastes metal refineries, natural erosion Natural erosion, water additive discharge from fertilizer and aluminum factories Fluoride 1.06 to 1.17 4 MCLG = Maximum contaminant level goal For each substance, estimate the standard deviation 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 Fluoride

Explanation / Answer

here as for uniform distirbution std deviaiton =range/(12)1/2

and for normal distribution std deviaiton =range/4

therefore

substance uniform distribution normal distribution chromium chromium 0.0548 0.0475 Barium Barium 0.0038 0.0033 Fluoride Fluoride 0.0318 0.0275

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