High concentration of the toxic element arsenic is all toocommon in groundwater. The

Chapter 7, Problem 52

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High concentration of the toxic element arsenic is all toocommon in groundwater. The article Evaluation ofTreatment Systems for the Removal of Arsenic fromGroundwater (Practice Periodical of Hazardous,Toxic, and Radioactive Waste Mgmt., 2005: 152157)reported that for a sample of n 5 5 water specimensselected for treatment by coagulation, the sample meanarsenic concentration was 24.3 mg/L, and the samplestandard deviation was 4.1. The authors of the citedarticle used t-based methods to analyze their data, sohopefully had reason to believe that the distribution ofarsenic concentration was normal.a. Calculate and interpret a 95% CI for true averagearsenic concentration in all such water specimens.b. Calculate a 90% upper confidence bound for the standard deviation of the arsenic concentrationdistribution.c. Predict the arsenic concentration for a single waterspecimen in a way that conveys information aboutprecision and reliability.