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Nambe Mills manufactures a line of metal tableware called Nambeware. A piece of Nambeware is produced by sand casting a special alloy of several metals. After casting, the piece goes through a series of shaping, grinding, buffing, and polishing steps. As part of a study of its production process, Nambe Mills wants to estimate the mean polishing time of its Nambeware pieces. It selects a random sample of 40 pieces and collects data on their polishing times. The sample standard deviation s is used to estimate o. The project manager uses the sample data to draw conclusions about the distribution of the population of polishing times for Nambeware pieces. He calculates the skewness and obtains a value of -1.65. He also examines the histogram of the sample data (shown below). 16 14 FREQUENCY 12 10 20 40 60 80 100 120 140 160 180 POLISHING TIME (Minutes) The sample data the conclusion that the distribution of the population is normal. The sample data also suggest that the population is The sample size is to provide a good approximate confidence interval. not adequate adequate