Question

A random sample of 125 items is drawn from a population whose standard deviation is known to be σ = 30. The sample mean is  x¯ = 860.

(a)	Construct an interval estimate for μ with 95 percent confidence. (Round your answers to 1 decimal place.)

  The 95% confidence interval is from _________ to __________

(b)	Construct an interval estimate for μ with 95 percent confidence, assuming that σ = 60. (Round your answers to 1 decimal place.)

  The 95% confidence interval is from ________ to ____________

(c)	Construct an interval estimate for μ with 95 percent confidence, assuming that σ = 120. (Round your answers to 1 decimal place.)

  The 95% confidence interval is from _________ to ____________

(d)	Describe how the confidence interval changes as σ increases.
	The interval stays the same as σ increases. The interval gets wider as σ increases. The interval gets narrower as σ increases. The interval gets wider as σ decreases.

Answer 1