tailieunhanh - Ebook Business statistics in practice (7th edition): Part 2

(BQ) Part 2 book "Business statistics in practice" has contents: Comparing two means and two proportions, statistical inferences for population variances, experimental design and analysis of variance, simple linear regression analysis, multiple regression and model building, time series forecasting and index numbers,.and other contents. | 11/29/12 2:29 PM Page 380 CHAPTER 10 Comparing Two Means and Two Proportions Learning Objectives After mastering the material in this chapter, you will be able to: LO10-1 Compare two population means when the samples are independent. LO10-2 Recognize when data come from independent samples and when they are paired. Chapter Outline Comparing Two Population Means by Using Independent Samples Paired Difference Experiments LO10-3 Compare two population means when the data are paired. LO10-4 Compare two population proportions using large independent samples. Comparing Two Population Proportions by Using Large, Independent Samples 12/3/12 11:53 AM Page 381 B population means and two population proportions. We make these comparisons by studying differences. For instance, to compare two population means, say m1 and m2, we consider the difference between these means, m1 Ϫ m2. If, for example, we use a confidence interval or hypothesis test to conclude that m1 Ϫ m2 is a positive number, then we conclude that m1 is greater than m2. On the other hand, if a confidence interval or hypothesis test shows that m1 Ϫ m2 is a negative number, then we conclude that m1 is less than m2. We explain many of this chapter’s methods in the context of three new cases: usiness improvement often requires making comparisons. For example, to increase consumer awareness of a product or service, it might be necessary to compare different types of advertising campaigns. Or to offer more profitable investments to its customers, an investment firm might compare the profitability of different investment portfolios. As a third example, a manufacturer might compare different production methods in order to minimize or eliminate out-ofspecification product. In this chapter we discuss using confidence intervals and hypothesis tests to compare two populations. Specifically, we compare .