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Lecture Basic statistics for business and economics - Chapter 9: Estimation and confidence intervals

When you have completed this chapter, you will be able to: Define a point estimate, define confidence interval, compute a confidence interval for the population mean when the population standard deviation is known, compute a confidence interval for a population mean when the population standard deviation is unknown,. | Estimation and Confidence Intervals Chapter 09 Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin LEARNING OBJECTIVES LO 9-1 Define a point estimate. LO 9-2 Define confidence interval. LO 9-3 Compute a confidence interval for the population mean when the population standard deviation is known. LO 9-4 Compute a confidence interval for a population mean when the population standard deviation is unknown. LO 9-5 Compute a confidence interval for a population proportion. LO 9-6 Calculate the required sample size to estimate a population proportion or population mean. 9- Sampling and Estimates Why Use Sampling? To contact the entire population is too time consuming. The cost of studying all the items in the population is often too expensive. The sample results are usually adequate. Certain tests are destructive. Checking all the items is physically impossible. Point Estimate versus Confidence Interval Estimate A point estimate is a single value (point) derived from a sample and used to estimate a population value. A confidence interval estimate is a range of values constructed from sample data so that the population parameter is likely to occur within that range at a specified probability. The specified probability is called the level of confidence. What are the factors that determine the width of a confidence interval? 1.The sample size, n. 2.The variability in the population, usually σ estimated by s. 3.The desired level of confidence. LO 9-1 Define a point estimate. 9- Interval Estimates – Interpretation For a 95% confidence interval about 95% of the similarly constructed intervals will contain the parameter being estimated. Also 95% of the sample means for a specified sample size will lie within 1.96 standard deviations of the hypothesized population LO 9-2 Define a confidence estimate. 9- How to Obtain z Value for a Given Confidence Level The 95 percent confidence refers to the middle 95 percent of | Estimation and Confidence Intervals Chapter 09 Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin LEARNING OBJECTIVES LO 9-1 Define a point estimate. LO 9-2 Define confidence interval. LO 9-3 Compute a confidence interval for the population mean when the population standard deviation is known. LO 9-4 Compute a confidence interval for a population mean when the population standard deviation is unknown. LO 9-5 Compute a confidence interval for a population proportion. LO 9-6 Calculate the required sample size to estimate a population proportion or population mean. 9- Sampling and Estimates Why Use Sampling? To contact the entire population is too time consuming. The cost of studying all the items in the population is often too expensive. The sample results are usually adequate. Certain tests are destructive. Checking all the items is physically impossible. Point Estimate versus Confidence Interval Estimate A point estimate is a single