A random sample of 11 items is drawn from a population whose standard deviation is unknown. The sample mean isx= 810 and the sample standard deviation is s = 20. Use Appendix D to find the values of Student's t.

(a) Construct an interval estimate of with 98% confidence. (Round your answers to 3 decimal places.)

The 98% confidence interval is from___to___

(b) Construct an interval estimate of with 98% confidence, assuming that s = 40. (Round your answers to 3 decimal places.)

The 98% confidence interval is from___to___

(c) Construct an interval estimate of with 98% confidence, assuming that s = 80. (Round your answers to 3 decimal places.)

The 98% confidence interval is from___to___