Twenty observations on etch uniformity on silicon wafers are taken during a qualification experiment for a plasma etcher. The data are as follows: 5.34, 6.65, 4.76, 5.98 7.25, 6.00, 7.55, 5.54, 5.62, 6.21 5.97, 7.35, 5.44, 4.39, 4.98, 5.25, 6.35, 4.61, 6.00, 5.32 a) Construct a 95 percent confidence interval estimate of σ2.