A random sample of 11 items is drawn from a population whose standard deviation is unknown. The sample mean is x = 920 and the sample standard deviation is s = 25. Use Appendix D to find the values of students' t.

(a) Construct an interval estimate of u with 95% confidence. (Round your answers to 3 decimal places)

The 95% confidence interval is from __________ to __________

(b) Construct an interval estimate of u with 95% confidence, assuming that s = 50.

(Round your answer to 3 decimal places.)

The 95% confidence interval is from __________ to ___________

(c) Construct an interval estimate of u with 95% confidence, assuming that s = 100.

(Round your answer to 3 decimal places.)

The 95% confidence interval is from ____________ to _________