Exercise 4: Confidence Intervals for the Population Means using z-values manufacturer of widgets expects that each widget will be 11 inches long (u= 11 inches). The population standard deviation (o) is thought to be 0.02 inch. The Sample Mean, X, is 10.998 inches. The sample size is 100. Inputs Sample Mean (X) Presumed Population Standard Deviation, Sample size (n) $ 10.998 0.02 inch 100 1. What is the point estimate for the population mean, ? 2. What is the appropriate z-value to use when constructing a confidence interval at a 95% and 99% confidence levels? Use the z-value table and Microsoft Excel. Confidence Level 95% (0.90) z-Value z-Value (Table) (Excel) 99% (0.99) Excel Formula =ABS(NORM.S.INV(0.025)) =ABS(NORM.S.INV(0.005)) 3. Using a z-values calculate the confidence interval using at a 95% and 99% confidence levels. Do this by hand and use Excel's CONFIDENCE.NORM function. Report the Margin of Error, Lower Confidence Limit, and Upper Confidence Limit. Paste your work from Excel using Word's Paste Special function. 4. What does these confidence intervals you constructed tell you