a random sample of 130 items is drawn from a population whose standard deviation is known to be o=60. The sample mean is x=70.

a) Construct an interval estimate for u with 95 percent confidence. (round to 1 decimal place)

The 95% confidence interval is from to

b) Construct an interval estimate for u with 95 percent confidence, assuming that o-120.

The 95% confidence interval is from to

c) Construct an interval estimate for u with 95 percent confidence that o=240.

The 95% confidence interval is from to

d) Describe how the confidence interval changes as o increases.