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 MCLG Range Detected Allowable MCLG Origin of Substance Chromium 0.46 to 0.64 100 Discharge from steel and pulp mills, natural erosion Barium 0.003 to 0.016 2 Discharge from drilling wastes, metal refineries, natural erosion Fluoride 1.05 to 1.20 4 Natural erosion, water additive, discharge from fertilizer and aluminum factories MCLG = Maximum contaminant level goal For each substance, estimate the standard deviation by assuming uniform distribution and normal distribution. (Round your answers to 4 decimal places.)

Uniform Distribution Normal Distribution

Chromium

Barium

Fluoride

Explanation / Answer

as we know for uniform distirbution std deviation =range/sqrt(12) and for normal distirbution std deviation =range/4

Uniform Distribution Normal Distribution   Chromium 0.0520 0.0450   Barium 0.0038 0.0033   Fluoride 0.0433 0.0375

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