About the Author |
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xv | |
Preface |
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xvii | |
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1 | (32) |
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1.1 Statistical Computing |
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3 | (1) |
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3 | (5) |
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1.2.1 Means Versus Correlations |
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3 | (4) |
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7 | (1) |
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1.2.3 Response Variable Assumptions |
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8 | (1) |
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1.3 Conceptual Overview of Linear Mixed Effects Regression |
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8 | (11) |
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9 | (4) |
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13 | (5) |
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1.3.3 How Important Are Random Effects? |
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18 | (1) |
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1.4 Traditional Approaches |
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19 | (2) |
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21 | (2) |
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23 | (4) |
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1.7 LMER and Multimodel Inference |
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27 | (5) |
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1.7.1 Statistical Hypotheses |
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27 | (5) |
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1.8 Overview of the Remainder of the Book |
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32 | (1) |
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2 Brief Introduction to R |
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33 | (30) |
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2.1 Obtaining and Installing R |
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34 | (1) |
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2.2 Functions and Packages |
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35 | (1) |
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36 | (5) |
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2.3.1 Prompt Versus Script Files |
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36 | (1) |
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2.3.2 Input and Output Appearance in This Book |
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36 | (1) |
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37 | (1) |
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2.3.4 Terminating a Process |
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37 | (1) |
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38 | (1) |
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38 | (1) |
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39 | (1) |
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2.3.8 Statistical Functions |
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40 | (1) |
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41 | (3) |
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43 | (1) |
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2.5 Matrices, Data Frames, and Lists |
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44 | (5) |
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44 | (1) |
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45 | (1) |
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45 | (1) |
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46 | (3) |
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49 | (5) |
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2.6.1 Matrix and Data Frame |
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49 | (1) |
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50 | (1) |
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51 | (1) |
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52 | (1) |
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52 | (1) |
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53 | (1) |
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2.6.7 Loading and Listing Objects |
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53 | (1) |
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2.7 User-Defined Functions |
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54 | (1) |
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2.8 Repetitive Operations |
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55 | (4) |
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55 | (2) |
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57 | (2) |
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59 | (2) |
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61 | (1) |
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2.11 Summary of Functions |
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61 | (2) |
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3 Data Structures and Longitudinal Analysis |
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63 | (42) |
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3.1 Longitudinal Data Structures |
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63 | (2) |
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64 | (1) |
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64 | (1) |
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3.2 Reading an External File |
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65 | (7) |
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3.2.1 Reading a Text File With read. table () |
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65 | (3) |
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3.2.2 Displaying the Data Frame |
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68 | (2) |
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3.2.3 Converting and Recoding Variables |
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70 | (2) |
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3.3 Basic Statistics for Wide-Format Data |
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72 | (4) |
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3.3.1 Means, Variances, and Correlations |
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73 | (1) |
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3.3.2 Missing Data Statistics |
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74 | (1) |
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3.3.3 Conditioning on Static Predictors |
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75 | (1) |
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76 | (4) |
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3.4.1 Wide to Long Format |
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76 | (3) |
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3.4.2 Long to Wide Format |
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79 | (1) |
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3.5 Basic Statistics for Long-Format Data |
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80 | (4) |
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3.5.1 Means, Variances, and Correlations |
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80 | (2) |
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3.5.2 Missing Data Statistics |
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82 | (1) |
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3.5.3 Conditioning on Static Predictors |
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82 | (2) |
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3.6 Data Structures and Balance on Time |
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84 | (1) |
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3.7 Missing Data in LMER Analysis |
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85 | (4) |
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3.7.1 Retain or Omit Missing Data Rows? |
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88 | (1) |
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3.8 Missing Data Concepts |
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89 | (11) |
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3.8.1 Missing Completely at Random |
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90 | (1) |
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91 | (1) |
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3.8.3 Not Missing at Random |
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92 | (1) |
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3.8.4 Missing Data Mechanisms and Statistical Analysis |
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93 | (1) |
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3.8.5 Missing Data Simulation |
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94 | (3) |
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97 | (3) |
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3.9 Extensions to More Complex Data Structures |
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100 | (5) |
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3.9.1 Multiple Dynamic Variables |
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100 | (2) |
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102 | (3) |
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4 Graphing Longitudinal Data |
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105 | (42) |
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4.1 Graphing and Statistical Strategy |
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105 | (1) |
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4.2 Graphing With ggplot2 |
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106 | (3) |
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107 | (1) |
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107 | (2) |
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4.3 Graphing Individual-Level Curves |
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109 | (13) |
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4.3.1 Superimposed Individual Curves |
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109 | (3) |
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4.3.2 Facet Plots of Individual Curves |
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112 | (1) |
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113 | (2) |
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4.3.4 Graphing Fitted Curves |
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115 | (7) |
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4.4 Graphing Group-Level Curves |
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122 | (8) |
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123 | (3) |
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4.4.2 Graphing Fitted Curves |
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126 | (3) |
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4.4.3 Graphing Individual-Level and Group-Level Curves |
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129 | (1) |
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4.5 Conditioning on Static Predictors |
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130 | (13) |
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4.5.1 Categorical Static Predictors |
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132 | (7) |
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4.5.2 Quantitative Static Predictors |
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139 | (4) |
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143 | (2) |
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143 | (1) |
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144 | (1) |
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4.6.3 Customizing the Legend |
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144 | (1) |
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4.7 Summary of ggplot2 Components |
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145 | (2) |
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5 Introduction to Linear Mixed Effects Regression |
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147 | (44) |
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5.1 Traditional Regression and the Linear Model |
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148 | (2) |
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150 | (10) |
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5.2.1 Single Quantitative Predictor |
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150 | (4) |
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5.2.2 Analysis of Covariance |
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154 | (4) |
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158 | (2) |
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5.3 Linear Mixed Effects Regression |
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160 | (10) |
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5.3.1 LMER as a Multilevel Model |
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163 | (4) |
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5.3.2 Random Effects as Errors |
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167 | (1) |
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5.3.3 Assumptions Regarding Random Effects and Random Error |
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168 | (1) |
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5.3.4 Random Effects and Correlated Observations |
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169 | (1) |
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5.4 Estimating the LMER Model |
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170 | (7) |
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5.4.1 Time as a Predictor |
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170 | (5) |
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5.4.2 Anchoring the Intercept |
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175 | (2) |
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5.5 LMER With Static Predictors |
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177 | (4) |
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177 | (1) |
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5.5.2 Slope and Intercept Effects |
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178 | (1) |
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5.5.3 Initial Status as a Static Predictor |
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179 | (1) |
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5.5.4 Extensions to More Complex Models |
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180 | (1) |
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5.5.5 Summary of lmer () Syntax |
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181 | (1) |
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5.6 Additional Details of LMER |
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181 | (10) |
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5.6.1 General Form of the LMER Model |
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182 | (2) |
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5.6.2 Variance-Covariance Matrix Among Repeated Measures |
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184 | (2) |
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5.6.3 Importance of Random Effects |
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186 | (1) |
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5.6.4 Working With Matrices in R |
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187 | (4) |
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6 Overview of Maximum Likelihood Estimation |
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191 | (36) |
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192 | (2) |
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6.2 Maximum Likelihood and LM |
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194 | (18) |
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6.2.1 Several Unknown Parameters |
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202 | (2) |
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6.2.2 Exhaustive Search and Numerical Methods |
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204 | (3) |
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6.2.3 Restricted Maximum Likelihood |
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207 | (1) |
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6.2.4 Extracting the Log-Likelihood and the Deviance |
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208 | (1) |
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208 | (4) |
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6.3 Maximum Likelihood and LMER |
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212 | (12) |
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6.3.1 LMER Deviance Function |
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214 | (2) |
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216 | (4) |
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6.3.3 Additional SE Details |
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220 | (2) |
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6.3.4 Default lmer () Output |
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222 | (1) |
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6.3.5 Assumptions Regarding Missing Data |
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223 | (1) |
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6.4 Additional Details of ML for LMER |
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224 | (3) |
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7 Multimodel Inference and Akaike's Information Criterion |
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227 | (58) |
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228 | (4) |
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232 | (3) |
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7.3 AIC and Predictive Accuracy |
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235 | (11) |
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243 | (2) |
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245 | (1) |
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246 | (8) |
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246 | (2) |
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248 | (4) |
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252 | (2) |
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7.5 AICc and Multimodel Inference |
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254 | (6) |
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255 | (5) |
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7.6 Example of Multimodel Analysis |
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260 | (15) |
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7.6.1 Guidelines for Model Formulation |
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260 | (1) |
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7.6.2 Example Set of Models |
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261 | (3) |
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7.6.3 Bar Graphs of Results |
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264 | (1) |
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7.6.4 Interpretation of Global Results |
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265 | (3) |
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268 | (5) |
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7.6.6 Comments Regarding the Multimodel Approach |
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273 | (1) |
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273 | (2) |
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275 | (2) |
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7.8 Parametric Bootstrap of the Evidence Ratio |
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277 | (5) |
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7.8.1 Performing the Parametric Bootstrap |
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278 | (4) |
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7.8.2 Caveats Regarding the Parametric Bootstrap |
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282 | (1) |
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7.9 Bayesian Information Criterion |
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282 | (3) |
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285 | (36) |
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8.1 Why Use the Likelihood Ratio Test? |
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286 | (2) |
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8.2 Fisher and Neyman-Pearson |
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288 | (3) |
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8.3 Evaluation of Two Nested Models |
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291 | (10) |
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8.3.1 Calibrating p-Values Based on Predictive Accuracy |
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295 | (6) |
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8.4 Approaches to Testing Multiple Models |
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301 | (1) |
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302 | (5) |
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306 | (1) |
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8.5.2 Comments on the Step-Up Approach |
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307 | (1) |
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307 | (3) |
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8.7 Comparison of Approaches |
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310 | (2) |
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312 | (4) |
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8.8.1 Comments on the Parametric Bootstrap |
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315 | (1) |
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316 | (5) |
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8.9.1 Comment on the Procedure |
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320 | (1) |
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9 Selecting Time Predictors |
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321 | (36) |
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9.1 Selection of Time Transformations |
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322 | (3) |
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9.2 Group-Level Selection of Time Transformations |
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325 | (1) |
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326 | (7) |
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9.3.1 Analysis Without Static Predictors |
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327 | (2) |
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9.3.2 Analysis With Static Predictors |
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329 | (4) |
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9.4 Likelihood Ratio Test |
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333 | (2) |
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9.4.1 Analysis Without Static Predictors |
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333 | (2) |
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9.4.2 Analysis With Static Predictors |
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335 | (1) |
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9.5 Cautions Concerning Group-Level Selection |
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335 | (1) |
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9.6 Subject-Level Selection of Time Transformations |
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336 | (21) |
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9.6.1 Level 1 Polynomial Model |
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336 | (1) |
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337 | (1) |
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338 | (8) |
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9.6.4 Pooled Measures of Fit |
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346 | (4) |
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9.6.5 Clustering of Subject Curves |
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350 | (7) |
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10 Selecting Random Effects |
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357 | (48) |
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10.1 Automatic Selection of Random Effects |
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358 | (1) |
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10.2 Random Effects and Variance Components |
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359 | (12) |
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10.2.1 Restricted Maximum Likelihood |
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361 | (2) |
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10.2.2 Random Effects and Correlated Data |
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363 | (8) |
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371 | (12) |
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372 | (4) |
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10.3.2 Examining Residuals |
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376 | (6) |
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10.3.3 Residuals and Normality |
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382 | (1) |
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383 | (11) |
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10.4.1 Likelihood Ratio Test |
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383 | (10) |
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393 | (1) |
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10.5 Variance Components and Static Predictors |
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394 | (1) |
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10.6 Predicted Random Effects |
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394 | (11) |
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10.6.1 Evaluating the Normality Assumption |
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397 | (2) |
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10.6.2 Predicted Values for an Individual |
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399 | (6) |
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11 Extending Linear Mixed Effects Regression |
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405 | (38) |
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11.1 Graphing Fitted Curves |
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405 | (4) |
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11.2 Static Predictors With Multiple Levels |
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409 | (11) |
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11.2.1 Evaluating Sets of Dummy Variables |
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415 | (1) |
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11.2.2 Evaluating Individual Dummy Variables |
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416 | (4) |
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11.3 Interactions Among Static Predictors |
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420 | (7) |
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11.3.1 Static Predictor Interactions With lmer () |
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422 | (2) |
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11.3.2 Interpreting Interactions |
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424 | (2) |
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11.3.3 Nonlinear Static Predictor Effects |
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426 | (1) |
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11.4 Indexes of Absolute Effect Size in LMER |
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427 | (6) |
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11.4.1 Alternative Indexes |
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429 | (4) |
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11.5 Additional Transformations |
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433 | (10) |
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11.5.1 Time Units and Variances |
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434 | (3) |
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11.5.2 Transforming for Standardized Change |
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437 | (2) |
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11.5.3 Standardizing and Compositing |
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439 | (4) |
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12 Modeling Nonlinear Change |
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443 | (46) |
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12.1 Data Set and Analysis Strategy |
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444 | (4) |
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12.2 Global Versus Local Models |
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448 | (1) |
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449 | (11) |
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12.3.1 Mean-Corrected Polynomials |
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454 | (1) |
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12.3.2 Orthogonal Polynomials |
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454 | (1) |
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12.3.3 The poly () Function |
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455 | (4) |
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12.3.4 Polynomial Example |
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459 | (1) |
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12.4 Alternatives to Polynomials |
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460 | (1) |
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12.5 Trigonometric Functions |
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461 | (5) |
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12.6 Fractional Polynomials |
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466 | (12) |
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12.6.1 First-Order Fractional Polynomials |
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467 | (4) |
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12.6.2 Second-Order Fractional Polynomials |
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471 | (3) |
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474 | (1) |
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12.6.4 Caveats Regarding the Use of Fractional Polynomials |
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475 | (3) |
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478 | (8) |
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12.7.1 Linear Spline Models |
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479 | (6) |
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12.7.2 Higher Order Regression Splines |
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485 | (1) |
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486 | (3) |
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12.8.1 Computing Orthogonal Polynomials |
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486 | (2) |
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12.8.2 General Form of Fractional Polynomials |
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488 | (1) |
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489 | (26) |
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490 | (10) |
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13.1.1 Dynamic Predictor as a Single Effect |
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493 | (3) |
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13.1.2 Dynamic Predictor With a Time Variable |
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496 | (4) |
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13.2 Multiple Response Variables |
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500 | (7) |
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13.2.1 Reading and Mathematics |
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500 | (1) |
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13.2.2 Analyzing Two Responses With lmer () |
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501 | (6) |
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13.3 Additional Levels of Nesting |
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507 | (8) |
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508 | (5) |
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13.3.2 Static Predictors in Three-Level Models |
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513 | (2) |
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Appendix: Soft Introduction to Matrix Algebra |
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515 | (10) |
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515 | (2) |
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517 | (1) |
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518 | (1) |
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A.4 Multiplication of a Matrix by a Scalar |
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518 | (1) |
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A.5 Matrix Multiplication |
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518 | (2) |
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520 | (1) |
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521 | (2) |
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A.8 Matrix Algebra and R Functions |
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523 | (2) |
References |
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525 | (10) |
Author Index |
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535 | (4) |
Subject Index |
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539 | |