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Upper and lower confidence intervals: Water treatment example

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Most water treatment facilities monitor the quality of their drinking water on an hourly basis. One variable monitored is pH, which measures the degree of alkalinity or acidity in the water. A target pH level is 8.5. pH values below 8.5 is acidic and above 8.5 is alkaline, both of which are bad for health. A random sample of 20 measurements resulted in an average pH of 8.55 with a standard deviation of 0.28.

a. Does the sample provide sufficient evidence that the mean pH level in the water differs from 8.5? Conduct a test at the ? = .01 level

b. What are the upper and lower limits of the 95% confidence intervals?

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Provides steps necessary to find the upper and lower confidence intervals.

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