(Solution) - The EPA limit on the allowable discharge of suspended solids -(2025 Original AI-Free Solution)

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The EPA limit on the allowable discharge of suspended solids into rivers and streams is 60 milligrams per liter (mg/l) per day. A study of water samples selected from the discharge at a phosphate mine shows that over a long period, the mean daily discharge of suspended solids is 48 mg/l, but day-to-day discharge readings are variable. State inspectors measured the discharge rates of suspended solids for n = 20 days and found s2 = 39 (mg/l)2. Find a 90% confidence interval for ?2. Interpret your results.