A random sample of 25 items is drawn from a population whose standard deviation is unknown. The sample mean isx

x

= 850 and the sample standard deviation iss= 15. UseAppendix Dto find the values of Student'st.

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

The 95% confidence interval is fromto

(b)Construct an interval estimate ofwith 95% confidence, assuming thats= 30.(Round your answers to 3 decimal places.)

The 95% confidence interval is fromto

(c)Construct an interval estimate ofwith 95% confidence, assuming thats= 60.(Round your answers to 3 decimal places.)

The 95% confidence interval is fromto