A random sample of 16 items is drawn from a population whose standard deviation is unknown. The sample mean isx

x= 890 and the sample standard deviation is s= 15. 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= 30.(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= 60.(Round your answers to 3 decimal places.)

The 95% confidence interval is from___ to ___