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Unformatted text preview: company sets the machine to attain an average of 75 ppm (parts per million) for the batches of water treated. They believe the machines output can be described by a Normal model with a standard deviation 4.2 ppm. a. What percent of the batches of water discharged exceed the 80 ppm standard? b. The companys lawyers insist that they not have more than 2% of the water over the limit. To what mean value should the company set the scrubbing machine? Assume the standard deviation does not change. c. Because achieving a mean that low would raise the costs too much, they decide to leave the mean set at 75 ppm and try to reduce the standard deviation to achieve the only 2% over goal. Find the new standard deviation needed. d. Explain what achieving a smaller standard deviation means in this context....
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- Spring '08
- Standard Deviation