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Acknowledgments xiii Foreword xxiii Introduction xxvii
Part One Thinking Like a Data Head
Chapter 1 What Is the Problem? 3 Questions a Data Head Should Ask 4 Why Is This Problem Important? 4 Who Does This Problem Affect? 6 What If We Don''t Have the Right Data? 6 When Is the Project Over? 7 What If We Don''t Like the Results? 7 Understanding Why Data Projects Fail 8 Customer Perception 8 Discussion 10 Working on Problems That Matter 11
Chapter Summary 11
Chapter 2 What Is Data? 13 Data vs. Information 13 An Example Dataset 14 Data Types 15 How Data Is Collected and Structured 16 Observational vs. Experimental Data 16 Structured vs. Unstructured Data 17 Basic Summary Statistics 18
Chapter Summary 19
Chapter 3 Prepare to Think Statistically 21 Ask Questions 22 There Is Variation in All Things 23 Scenario: Customer Perception (The Sequel) 24 Case Study: Kidney-Cancer Rates 26 Probabilities and Statistics 28 Probability vs. Intuition 29 Discovery with Statistics 31
Chapter Summary 33
Part Two Speaking Like a Data Head
Chapter 4 Argue with the Data 37 What Would You Do? 38 Missing Data Disaster 39 Tell Me the Data Origin Story 43 Who Collected the Data? 44 How Was the Data Collected? 44 Is the Data Representative? 45 Is There Sampling Bias? 46 What Did You Do with Outliers? 46 What Data Am I Not Seeing? 47 How Did You Deal with Missing Values? 47 Can the Data Measure What You Want It to Measure? 48 Argue with Data of All Sizes 48
Chapter Summary 49
Chapter 5 Explore the Data 51 Exploratory Data Analysis and You 52 Embracing the Exploratory Mindset 52 Questions to Guide You 53 The Setup 53 Can the Data Answer the Question? 54 Set Expectations and Use Common Sense 54 Do the Values Make Intuitive Sense? 54 Watch Out: Outliers and Missing Values 58 Did You Discover Any Relationships? 59 Understanding Correlation 59 Watch Out: Misinterpreting Correlation 60 Watch Out: Correlation Does Not Imply Causation 62 Did You Find New Opportunities in the Data? 63
Chapter Summary 63
Chapter 6 Examine the Probabilities 65 Take a Guess 66 The Rules of the Game 66 Notation 67 Conditional Probability and Independent Events 69 The Probability of Multiple Events 69 Two Things That Happen Together 69 One Thing or the Other 70 Probability Thought Exercise 72 Next Steps 73 Be Careful Assuming Independence 74 Don''t Fall for the Gambler''s Fallacy 74 All Probabilities Are Conditional 75 Don''t Swap Dependencies 76 Bayes'' Theorem 76 Ensure the Probabilities Have Meaning 79 Calibration 80 Rare Events Can, and Do, Happen 80
Chapter Summary 81
Chapter 7 Challenge the Statistics 83 Quick Lessons on Inference 83 Give Yourself Some Wiggle Room 84 More Data, More Evidence 84 Challenge the Status Quo 85 Evidence to the Contrary 86 Balance Decision Errors 88 The Process of Statistical Inference 89 The Questions You Should Ask to Challenge the Statistics 90 What Is the Context for These Statistics? 90 What Is the Sample Size? 91 What Are You Testing? 92 What Is the Null Hypothesis? 92 Assuming Equivalence 93 What Is the Significance Level? 93 How Many Tests Are You Doing? 94 Can I See the Confidence Intervals? 95 Is This Practically Significant? 96 Are You Assuming Causality? 96
Chapter Summary 97
Part Three Understanding the Data Scientist''s Toolbox
Chapter 8 Search for Hidden Groups 101 Unsupervised Learning 102 Dimensionality Reduction 102 Creating Composite Features 103 Principal Component Analysis 105 Principal Components in Athletic Ability 105 PCA Summary 108 Potential Traps 109 Clustering 110 k -Means Clustering 111 Clustering Retail Locations 111 Potential Traps 113
Chapter Summary 114
Chapter 9 Understand the Regression Model 117 Supervised Learning 117 Linear Regression: What It Does 119 Least Squares Regression: Not Just a Clever Name 120 Linear Regression: What It Gives You 123 Extending to Many Features 124 Linear Regression: What Confusion It Causes 125 Omitted Variables 125 Multicollinearity 126 Data Leakage 127 Extrapolation Failures 128 Many Relationships Aren''t Linear 128 Are You Explaining or Predicting? 128 Regression Performance 130 Other Regression Models 131
Chapter Summary 131
Chapter 10 Understand the Classification Model 133 Introduction to Classification 133 What You''ll Learn 134 Classification Problem Setup 135 Logistic Regression 135 Logistic Regression: So What? 138 Decision Trees 139 Ensemble Methods 142 Random Forests 143 Gradient Boosted Trees 143 Interpretability of Ensemble Models 145 Watch Out for Pitfalls 145 Misapplication of the Problem 146 Data Leakage 146 Not Splitting Your Data 146 Choosing the Right Decision Threshold 147 Misunderstanding Accuracy 147 Confusion Matrices 148
Chapter Summary 150
Chapter 11 Understand Text Analytics 151 Expectations of Text Analytics 151 How Text Becomes Numbers 153 A Big Bag of Words 153 N-Grams 157 Word Embeddings 158 Topic Modeling 160 Text Classification 163 Naïve Bayes 164 Sentiment Analysis 166 Practical Considerations When Working with Text 167 Big Tech Has the Upper Hand 168
Chapter Summary 169
Chapter 12 Conceptualize Deep Learning 171 Neural Networks 172 How Are Neural Networks Like the Brain? 172 A Simple Neural Network 173 How a Neural Network Learns 174 A Slightly More Complex Neural Network 175 Applications of Deep Learning 178 The Benefits of Deep Learning 179 How Computers "See" Images 180 Convolutional Neural Networks 182 Deep Learning on Language and Sequences 183 Deep Learning in Practice 185 Do You Have Data? 185 Is Your Data Structured? 186 What Will the Network Look Like? 186 Artificial Intelligence and You 187 Big Tech Has the Upper Hand 188 Ethics in Deep Learning 189
Chapter Summary 190
Part Four Ensuring Success
Chapter 13 Watch Out for Pitfalls 193 Biases and Weird Phenomena in Data 194 Survivorship Bias 194 Regression to the Mean 195 Simpson''s Paradox 195 Confirmation Bias 197 Effort Bias (aka the "Sunk Cost Fallacy") 197 Algorithmic Bias 198 Uncategorized Bias 198 The Big List of Pitfalls 199 Statistical and Machine Learning Pitfalls 199 Project Pitfalls 200
Chapter Summary 202
Chapter 14 Know the People and Personalities 203 Seven Scenes of Communication Breakdowns 204 The Postmortem 204 Storytime 205 The Telephone Game 206 Into the Weeds 206 The Reality Check 207 The Takeover 207 The Blowhard 208 Data Personalities 208 Data Enthusiasts 209 Data Cynics 209 Data Heads 209
Chapter Summary 210
Chapter 15 What''s Next? 211 Index 215