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

x= 830 and the sample standard deviation iss= 5. 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= 10.(Round your answers to 3 decimal places.)

The 95% confidence interval is from ?to?

(c)Construct an interval estimate ofwith 95% confidence, assuming thats= 20.(Round your answers to 3 decimal places.)

The 95% confidence interval is from?to?

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

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