Chapter 3. Describing Data from a Single Variable

3.1 Introduction 54

3.1.1 Graphs for Continuous Data 54

3.1.2 Numerical Summaries for Continuous Data 55

3.1.3 Data Descriptions for Nominal and Ordinal Data 56

3.2 Example: Order Processing in an Herbal Tea Mail Order Business 57

3.3 Descriptive Statistics with the JMP Distribution Platform 58

3.3.1 Describing a Continuous Variable 58

3.3.2 Describing a Nominal Variable 62

3.4 Interpretation of Descriptive Statistics 64

3.4.1 Histogram 64

3.4.2 Box Plot 65

3.4.3 CDF Plot 67

3.4.4 Quantiles 69

3.4.5 Moments 70

3.5 Practical Advice and Potential Problems 71 3.5.1 Features of Good Graphs 71

3.5.2 Example: Izod Impact Strength of Two Suppliers 71

3.5.3 Simple Improvements to Histograms 72

3.5.4 Potential Problems with Box Plots and Histograms 74

3.6 Summary 76

3.7 Problems 77

3.8 Case Study: New Web Software Testing 79