Finding Missing Data A journal article includes a graph showing that sample data are normally distributed.

a. The confidence level is inadvertently omitted when this confidence interval is given: 2.8 , s , 6.0. Find the confidence level for these given sample statistics:

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b. This 95% confidence interval is given: 19.1 , s , 45.8. Given n 5 12, find the value of the standard deviation s, which was omitted from the article.