Guide to Using Excel For Basic Statistical Applications To Accompany Business Statistics: A Decision Making Approach, 6th Ed. Chapter 7: Estimating Population Values By Groebner, Shannon, Fry, & Smith Prentice-Hall Publishing Company Copyright, 2005

Chapter 7 Excel Examples  Interval Estimation - Interval Estimation - Nagel Beverage Company  Interval Estimation - Interval Estimation - Heritage Software

Interval Estimation- Nagel Beverage Company Issue: The manager is interested in estimating the mean fill amount in soft-drink cans. Ideal average is 12 ounces Objective: Use Excel to help construct a confidence interval estimate for population mean fill volume. Data file is Nagel-Beverage.xls

Open File Nagel-Beverage.xls File contains sample data for 100 cans – last row is 101 Interval Estimation – Nagel Beverage

First Step is to develop a histogram for the sample data. Define Bins (upper limit of each class) Interval Estimation – Nagel Beverage

Click on Tools – then Data Analysis – then Histogram Interval Estimation – Nagel Beverage

Complete the Histogram Wizard - Note, check Chart Output. Placing output on a new worksheet is optional. Interval Estimation – Nagel Beverage

This is Excel’s default histogram – See the Capital Credit Union example in Chapter 2 for the specific steps to improve the histogram Interval Estimation – Nagel Beverage

Distribution for the sample data – looks to be spread fairly evenly around 12 ounces. Need to compute a confidence interval estimate. Interval Estimation – Nagel Beverage

Click on Tools – then Data Analysis – then Descriptive Statistics Interval Estimation – Nagel Beverage

Define data range, output location and check Summary Statistics option and Confidence Level for Mean. Interval Estimation – Nagel Beverage

95 % Confidence Interval = Margin of Error for 95% confidence interval Interval Estimation – Nagel Beverage

Interval Estimation - Heritage Software Issue: The company has service representatives who answer calls from customers. The managers are interested in estimating the mean call time Objective: Use Excel to help construct a confidence interval estimate for population mean call time. Data file is Heritage.xls

Open File Heritage.xls File contains sample data for 25 calls – last row is 26. Interval Estimation – Heritage Software

Click on Tools – then Data Analysis – then Descriptive Statistics Interval Estimation – Heritage Software

Define data range, output location and check Summary Statistics option and Confidence Level for Mean. Interval Estimation – Heritage Software

95 % Confidence Interval = Margin of Error for 95% confidence interval Interval Estimation – Heritage Software

PHStat Option: Select PHStat tab, then Confidence Intervals – then Estimate for the Mean, sigma unknown Interval Estimation – Heritage Software

Specify Confidence Level, data range, and title. Interval Estimation – Heritage Software

PHStat results Interval Estimation – Heritage Software