The EPA wants to test a randomly selected sample of n water specimens and estimate the mean daily rate of pollution produced by a mining operation. If the EPA wants a 80% confidence interval with a bound of error of 0.5 milligram per liter (mg/L), how many water specimens are required in the sample? Assume prior knowledge indicates that pollution readings in water samples taken during a day have been approximately normally distributed with a standard deviation of 4.1 (mg/L).
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We are given a confidence level of 80%, which means the z-score corresponding to this confidence level is 1.28 (you can find this value in a standard normal distribution table or using a calculator). Show more…
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