Please help me to understand this problem:

The diameter of steel rods manufactured on two different extrusion machines is being investigated. Two random samples of sizes my=13 and n2=16 are selected, and the sample means and sample variances are X1 = 8. /3, $1 = 0.30, X2 = 8.68, $5 = 0.40, respectively. Assume that the data are drawn from a normal distribution. Construct the following (using only Table VI of Appendix A): (a) A 90% two-sided CI on U1 / 02. Round your answers to 3 decimal places. CI: [ (b) A 95% two-sided CI on 1 / 02. Round your answers to 3 decimal places. CI: [ Which of the following is a true statement regarding the widths of the 90% and 95% CIs? 1. The width of the 95% CI is larger because we have more confidence in the 95% interval. 2. The width of the 95% CI is larger because there is a greater probability that it contains the true ratio of standard deviations. 3. The 90% CI is better since it has smaller width than the 95% CI. 4. The 95% CI is wider because it is 5% more likely to contain the true ratio of standard deviations. True statement: 3. Y (c) A 90% lower-confidence bound on 01/ 02. Round your answer to 3 decimal places. Lower-confidence bound =