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10. Statistical Inference for Two Samples. CHAPTER OUTLINE. 10-1 Inference on the Difference in Means of Two Normal Distributions, Variances Known 10-1.1 Hypothesis tests on the difference of means, variances known 10-1.2 Type II error and choice of sample size
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10 Statistical Inference for Two Samples CHAPTER OUTLINE 10-1 Inference on the Difference in Means of Two Normal Distributions, Variances Known 10-1.1 Hypothesis tests on the difference of means, variances known 10-1.2 Type II error and choice of sample size 10-1.3 Confidence interval on the difference in means, variance known 10-2 Inference on the Difference in Means of Two Normal Distributions, Variance Unknown 10-2.1 Hypothesis tests on the difference of means, variances unknown 10-2.2 Type II error and choice of sample size 10-2.3 Confidence interval on the difference in means, variance unknown 10-3 A Nonparametric Test on the Difference of Two Means 10-4 Paired t-Tests 10-5 Inference on the Variances of Two Normal Populations 10-5.1 F distributions 10-5.2 Hypothesis tests on the ratio of two variances 10-5.3 Type II error and choice of sample size 10-5.4 Confidence interval on the ratio of two variances 10-6 Inference on Two Population Proportions 10-6.1 Large sample tests on the difference in population proportions 10-6.2 Type II error and choice of sample size 10-6.3 Confidence interval on the difference in population proportions 10-7 Summary Table and Roadmap for Inference Procedures for Two Samples
Learning Objectives for Chapter 10 After careful study of this chapter, you should be able to do the following: • Structure comparative experiments involving two samples as hypothesis tests. • Test hypotheses and construct confidence intervals on the difference in means of two normal distributions. • Test hypotheses and construct confidence intervals on the ratio of the variances or standard deviations of two normal distributions. • Test hypotheses and construct confidence intervals on the difference in two population proportions. • Use the P-value approach for making decisions in hypothesis tests. • Compute power, Type II error probability, and make sample size decisions for two-sample tests on means, variances & proportions. • Explain & use the relationship between confidence intervals and hypothesis tests.
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Figure 10-1Two independent populations.
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Assumptions
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known 10-2.1 Hypothesis Tests for a Difference in Means, Variances Known
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Example 10-1
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Example 10-1
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Example 10-1
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known 10-2.2 Type II Error and Choice of Sample Size Use of Operating Characteristic Curves Two-sided alternative: One-sided alternative:
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known 10-2.2 Type II Error andChoice of Sample Size Sample Size Formulas Two-sided alternative:
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known 10-2.2 Type II Error and Choice of Sample Size Sample Size Formulas One-sided alternative:
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Example 10-3
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known 10-2.3 Confidence Interval on a Difference in Means, Variances Known Definition
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Example 10-4
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Example 10-4
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known Choice of Sample Size
10-2: Inference for a Difference in Means of Two Normal Distributions, Variances Known One-Sided Confidence Bounds Upper Confidence Bound Lower Confidence Bound
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 1: We wish to test:
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 1: The pooled estimator of 2:
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 1:
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Definition: The Two-Sample or Pooled t-Test*
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-5
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-5
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-5
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-5
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Minitab Output for Example 10-5
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Figure 10-2Normal probability plot and comparative box plot for the catalyst yield data in Example 10-5. (a) Normal probability plot, (b) Box plots.
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 2: is distributed approximately as t with degrees of freedom given by
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.1 Hypotheses Tests for a Difference in Means, Variances Unknown Case 2:
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-6
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-6 (Continued)
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-6 (Continued)
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-6 (Continued) Figure 10-3Normal probability plot of the arsenic concentration data from Example 10-6.
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Example 10-6 (Continued)
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.2 Type II Error and Choice of Sample Size Example 10-7
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Minitab Output for Example 10-7
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.3 Confidence Interval on the Difference in Means, Variance Unknown Case 1:
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Case 1: Example 10-8
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Case 1: Example 10-8 (Continued)
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Case 1: Example 10-8 (Continued)
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown Case 1: Example 10-8 (Continued)
10-3: Inference for a Difference in Means of Two Normal Distributions, Variances Unknown 10-3.3 Confidence Interval on the Difference in Means, Variance Unknown Case 2:
10-4: Paired t-Test • A special case of the two-sample t-tests of Section 10-3 occurs when the observations on the two populations of interest are collected in pairs. • Each pair of observations, say (X1j, X2j), is taken under homogeneous conditions, but these conditions may change from one pair to another. • The test procedure consists of analyzing the differences between hardness readings on each specimen.
10-4: Paired t-Test The Paired t-Test
10-4: Paired t-Test Example 10-10
10-4: Paired t-Test Example 10-10
10-4: Paired t-Test Example 10-10
10-4: Paired t-Test Paired Versus Unpaired Comparisons