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Chapter 9

Inferences Based on Two Samples

Confidence Intervals and Tests of Hypotheses

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9.1

Identifying the Target Parameter

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Procedure

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9.2

Comparing Two Population Means: Independent Sampling

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Table 9.1

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Figure 9.1 SPSS analysis of diet study data

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Figure 9.2 Sampling distribution of 1 2( )x x

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Definition

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Procedure

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Procedure

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Definition

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Figure 9.3 Rejection region for Example 9.2

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Figure 9.4 The observed significance level for Example 9.2

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Figure 9.5 Assumptions for the two-sample t; (1) normal populations; (2) equal variances

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Procedure

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Procedure

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Definition

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Table 9.2

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Figure 9.6 SAS printout for Example 9.4

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Figure 9.7 Normal probability plots for Example 9.4

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Figure 9.8 MINITAB box plots for Example 9.4

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Procedure

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Procedure

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Figure SIA9.1 MINITAB comparison of two price change means

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Figure SIA9.2 MINITAB comparison of two Trading volume means

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9.3

Comparing Two Population Means: Paired Difference Experiments

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Table 9.3

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Figure 9.9 MINITAB printout of an invalid analysis of reading test scores in 9.3

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Table 9.4

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Figure 9.10 Rejection region for Example 9.4

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Figure 9.11 MINITAB paired difference analysis of reading test scores

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Procedure

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Procedure

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Definition

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Definition

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Table 9.5

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Figure 9.12 SAS analysis of salary differences

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Figure 9.13 SPSS analysis of salaries, assuming independent samples

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Procedure

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9.4

Comparing Two Population Proportions: Independent Sampling

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Table 9.6

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Definition

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Procedure

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Procedure

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Definition

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Table 9.7

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Figure 9.14 Rejection region for Example 9.6

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Figure 9.15 MINITAB output for test of two proportions

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Figure SIA9.3 MINITAB comparison of two proportions analysis

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9.5

Determining the Sample Size

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Procedure

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Procedure

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Comparing Two Population Variances: Independent Sampling (Optional)

9.6

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Figure 9.16 An F-distribution with 7 numerator and 9 denominator degrees of freedom

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Table 9.8

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Figure 9.17 An F-distribution for 1 = 7 and 2 = 9 df; = .05

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Table 9.9

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Figure 9.18 MINITAB summary statistics and F-test for mice weights

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Figure 9.19 Rejection region for Example 9.10

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Procedure

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Procedure

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Definition

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Table 9.10

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Figure 9.20 SAS F-test for testing assumption of equal variances

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Procedure