Assume that each sample is obtained by randomly selecting values from a population with a normal distribution.
A journal article includes a graph showing that sample data are normally distributed.
a. The degree of confidence is inadvertently omitted when this confidence interval is given: 2.8 < σ < 6.0. Find the degree of confidence for these given sample statistics: n = 20, = 45.2, and σ = 3.8.
b. This 95% confidence interval is given: 19.1 < σ < 45.8. Find the value of the standard deviation s, which was omitted from the article.