11. Selenium A small amount of the trace element selenium, 502200 micrograms (mg) per day, is considered essential to good health. Suppose that a random sample of 30 adults was selected from each of two regions of the United States and that each person’s daily selenium intake was recorded. The means and standard deviations of the selenium daily intakes for the two groups are shown in the table.

Find a 95% confidence interval for the difference in the mean selenium intakes for the two regions. Interpret this interval.

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Region 1 2 Sample Mean (g) 167.1 140.9 Sample Standard Deviation (g) 24.3 17.6