A random sample of 26 items is drawn from a population whose standard deviation is unknown. The sample mean isx

x= 860 and the sample standard deviation iss= 20. 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 from______ to____

(b)Construct an interval estimate ofwith 95% confidence, assuming thats= 40.(Round your answers to 3 decimal places.)

The 95% confidence interval is from____ to _____

(c)Construct an interval estimate ofwith 95% confidence, assuming thats= 80.(Round your answers to 3 decimal places.)

The 95% confidence interval is from _____to _______