A random sample of 23 items is drawn from a population whose standard deviation is unknown. The sample mean isx

x= 840 and the sample standard deviation iss= 15. UseAppendix Dto find the values of Student'st.

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

The 98% confidence interval is from___to___

(b)Construct an interval estimate ofwith 98% confidence, assuming thats= 30.(Round your answers to 3 decimal places.)

The 98% confidence interval is from ___to___

(c)Construct an interval estimate ofwith 98% confidence, assuming thats= 60.(Round your answers to 3 decimal places.)

The 98% confidence interval is from___to___

(d)Describe how the confidence interval changes as s increases.

multiple choice

• The interval stays the same as s increases.
• The interval gets wider as s increases.
• Correct
• The interval gets narrower as s increases.