A random sample of 11 items is drawn from a population whose standard deviation is unknown. The sample mean is a = 920 and the sample standard deviation is s = 25. Use Appendix D to find the values of Student's t. (a) Construct an interval estimate of // with 95% confidence. (Round your answers to 3 decimal places.) The 95% confidence interval is from to (b) Construct an interval estimate of / with 95% confidence, assuming that s = 50. (Round your answers to 3 decimal places.) The 95% confidence interval is from to (c) Construct an interval estimate of // with 95% confidence, assuming that s= 100. (Round your answers to 3 decimal places.) The 95% confidence interval is from to (d) Describe how the confidence interval changes as s increases. O The interval stays the same as s increases. O The interval gets wider as s increases. O The interval gets narrower as s increases