v
Contents
Preface .........................................................................................................xvii
Acknowledgment ..........................................................................................xix
Introduction .................................................................................................xxi
Authors ...................................................................................................... xxiii
SECTION I DATA
1
Data, Data Quality, and Descriptive Statistics ......................................3
e Challenge at Persists .........................................................................3
Bringing Data to the Table Requires Motivation .........................................5
Data Quality ................................................................................................5
On Scales ............................................................................................5
Error ...................................................................................................6
Data Stratification ..............................................................................7
Visual Summary ..........................................................................................7
Numerical Descriptive Statistics (Numerical Summary of Data) ...............10
Special Statistics ...............................................................................12
ree Categories of Descriptive Statistics ..........................................12
Case Study: Interpretation of Effort Variance Descriptive Statistics ...........12
Application Notes ......................................................................................14
Concluding Remarks .................................................................................14
Review Questions ......................................................................................15
Exercises ....................................................................................................16
Appendix 1.1: Definition of Descriptive Statistics ......................................16
Number of Data Points .....................................................................16
Sum ..................................................................................................16
Variance ............................................................................................16
Standard Deviation ...........................................................................16
Maximum .........................................................................................17
Minimum .........................................................................................17
Range ...............................................................................................17
vi ◾ Contents
Mode ................................................................................................17
Median .............................................................................................17
Mean ................................................................................................18
Kurtosis (Flatness of Distribution) ....................................................18
Skewness (Skew of Distribution) .......................................................18
References ..................................................................................................18
Suggested Readings ...................................................................................19
2 Truth and Central Tendency ................................................................21
Mean .........................................................................................................21
Uncertainty in Mean: Standard Error ...............................................22
Median ......................................................................................................23
Mode .........................................................................................................25
Geometric Mean ........................................................................................25
Harmonic Mean ........................................................................................27
Interconnected Estimates ...........................................................................27
Weighted Mean .........................................................................................28
Robust Means ............................................................................................29
Trimmed Mean ................................................................................29
Winsorized Mean .............................................................................30
Midhinge ..........................................................................................30
Midrange ..........................................................................................30
Tukey’s Trimean ...............................................................................30
Mean Derived from Geometrical Perspectives ..................................30
Two Categories ..........................................................................................30
Category 1 ........................................................................................30
Category 2 ........................................................................................31
Truth .........................................................................................................31
Application Notes ......................................................................................32
Managing Software Projects Using Central Tendency Values ...........32
Making Predictions ..........................................................................32
Case Study: Shifting the Mean ..................................................................33
Review Questions ..................................................................................... 34
Exercises ................................................................................................... 34
References ................................................................................................. 34
Suggested Reading .................................................................................... 34
3 Data Dispersion ....................................................................................35
Range-Based Empirical Representation .....................................................35
Dispersion as Deviation from Center .........................................................38
Average Deviation .............................................................................39
Average Absolute Deviation ..............................................................39
Median Absolute Deviation ..............................................................39
Contents ◾ vii
Sum of Squares and Variance........................................................... 42
Standard Deviation .......................................................................... 44
Skewness and Kurtosis ...............................................................................45
Pearson’s Skewness ............................................................................45
Bowley’s Skewness ............................................................................45
ird Standardized Moment ............................................................45
Kurtosis ........................................................................................... 46
Coefficient of Dispersion............................................................................47
Coefficient of Range .........................................................................47
Coefficient of Quartile Deviation .....................................................47
Coefficient of Mean Deviation..........................................................48
Coefficient of MAD..........................................................................48
Coefficient of Standard Deviation ....................................................48
Summary of Coefficients of Dispersion .............................................48
Application Contexts .................................................................................49
In a Nutshell ..............................................................................................50
Measures of Dispersion .....................................................................50
Nature of Dispersion ........................................................................50
Coefficients of Dispersion .................................................................50
Case Study: Dispersion Analysis of Data Sample .......................................51
Review Questions ......................................................................................52
Exercises ....................................................................................................52
Reference ...................................................................................................52
Suggested Readings ...................................................................................52
4 Tukey’s Box Plot: Exploratory Analysis ...............................................53
e Structure of the Box Plot .....................................................................53
Customer Satisfaction Data Analysis Using the Box Plot ...........................55
Tailoring the Box Plot ................................................................................57
Applications of Box Plot.............................................................................57
Seeing Process Drift ..........................................................................58
Detecting Skew .................................................................................58
Seeing Variation ................................................................................58
Risk Measurement ............................................................................59
Outlier Detection .............................................................................59
Comparison of Processes ..................................................................59
Improvement Planning .....................................................................59
Core Benefits of Box Plot ...........................................................................60
Twin Box Plot ............................................................................................61
Holistic Test .....................................................................................62
Application Summary: Twin Box Plot .......................................................63
Case Study 1: Business Perspectives from CSAT Box Plots ....................... 64
CSAT Analysis across SBUs ............................................................. 64
viii ◾ Contents
Case Study 2: Process Perspectives from CSAT Box Plots ..........................65
CSAT Analysis across Attributes ...................................................... 66
Review Questions ..................................................................................... 66
Exercises ................................................................................................... 66
References ..................................................................................................67
SECTION II METRICS
5
Deriving Metrics ..................................................................................71
Creating Meaning in Data .........................................................................71
Deriving Metrics as a Key Performance Indicator ......................................71
Estimation and Metrics .............................................................................72
Paradigms for Metrics ................................................................................72
GQM Paradigm .........................................................................................73
Difficulties with Applying GQM to Designing a Metrics System ..............74
Need-Driven Metrics .................................................................................75
Meaning of Metrics: Interpreting Metric Data ..........................................76
Our Categories of Metrics..........................................................................78
Business Metrics ........................................................................................78
Project Metrics ...........................................................................................78
Process Metrics ..........................................................................................79
Subprocess Metrics ....................................................................................79
Product Metrics .........................................................................................80
Case Study: Power of Definitions ...............................................................80
Review Questions ......................................................................................82
Exercises ....................................................................................................82
References ..................................................................................................82
Suggested Readings ...................................................................................83
6 Achieving Excellence in Software Development Using Metrics ...........85
Examples of Project Metrics .......................................................................85
Time to Deliver ................................................................................85
Cost ..................................................................................................86
Quality .............................................................................................86
Productivity ......................................................................................86
Time to Repair .................................................................................86
Customer Satisfaction .......................................................................86
Requirement Volatility ......................................................................86
Examples of Product Metrics .....................................................................86
Requirement Size ..............................................................................86
Design Complexity ...........................................................................87
Code Size ..........................................................................................89
Code Complexity ............................................................................ 90
Contents ◾ ix
Defect Density ................................................................................. 90
Defect Classification .........................................................................91
Reliability .........................................................................................91
Examples of Process Metrics ......................................................................91
Review Effectiveness .........................................................................91
Test Effectiveness ..............................................................................91
Test Coverage ...................................................................................92
Subprocess Metrics ....................................................................................92
Converting Metrics into Business Information ..........................................93
Project Dashboard ............................................................................93
Product Health Report .....................................................................95
Statistical Process Control Charts .....................................................96
Case Study: Early Size Measurements ........................................................96
Project Progress Using Earned Value Metrics .............................................97
Tracking Progress .............................................................................97
Tracking Project Cost .......................................................................98
Review Questions ....................................................................................100
Exercises ..................................................................................................101
References ................................................................................................101
Suggested Readings .................................................................................102
7 Maintenance Metrics ..........................................................................103
Fusion of Frameworks in Software Maintenance .....................................103
Maintainability Index .....................................................................105
Change Requests Count .................................................................105
Customer Satisfaction Index ...........................................................106
Resource Utilization .......................................................................107
Service-Level Agreement Compliances ...........................................107
Percentage of On-Time Delivery .....................................................109
Enhancement Size ..........................................................................109
Bug Complexity ..............................................................................110
Effort Variance (EV) ....................................................................... 111
Schedule Variance (SV) ..................................................................111
Quality ...........................................................................................111
Quality of Enhancement ....................................................... 111
Quality of Bug Fix ................................................................. 111
Productivity ....................................................................................112
Time to Repair (TTR)....................................................................112
Backlog Index .................................................................................113
Bug Classification ...........................................................................113
Fix Quality .....................................................................................113
Refactoring Metrics ........................................................................113
Reliability .......................................................................................113
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