x ◾ Contents
Metric-Based Dashboards ........................................................................113
Review Questions .................................................................................... 115
Exercises ..................................................................................................115
References ................................................................................................ 115
Suggested Readings .................................................................................116
8 Software Test Metrics .........................................................................117
Project Metrics .........................................................................................117
Schedule Variance ...........................................................................117
Effort Variance ...............................................................................117
Cost ................................................................................................118
Human Productivity .......................................................................118
Requirement Stability .....................................................................118
Resource Utilization .......................................................................118
Customer Satisfaction .....................................................................119
Test Effectiveness ............................................................................119
Process Metrics ........................................................................................119
Defect Removal Efficiency ..............................................................120
Test Cases Count ............................................................................120
Test Coverage .................................................................................121
Functionality Coverage .........................................................121
Code Coverage ......................................................................121
Percentage of Bad Fix......................................................................122
Product Metrics .......................................................................................122
Defect Counts ................................................................................122
Defect Arrival Rate ................................................................122
Defect Closure Rate...............................................................122
Component Defect Count .....................................................123
Component Defect Density ............................................................123
Defect Classification .......................................................................124
Testing Size: Test Case Point ...................................................................124
Risk Metric ..............................................................................................125
Predicting Quality ...................................................................................126
Metrics for Test Automation ....................................................................126
Return on Investment .....................................................................126
Percentage Automatable ..................................................................126
Automation Progress .......................................................................127
Case Study: Defect Age Data ...................................................................127
Review Questions ....................................................................................128
Exercises ..................................................................................................129
References ................................................................................................129
Suggested Readings .................................................................................129
Contents ◾ xi
9 Agile Metrics ......................................................................................131
Classic Metrics: Unpopular Science .........................................................132
Two Sides of Classic Metrics ....................................................................133
Metrics for Agile: Humanization .............................................................134
e Price of Humanization ......................................................................134
Common Agile Metrics ...........................................................................135
Velocity ...........................................................................................135
Story Point ......................................................................................135
Technical Debt ...............................................................................136
Tests ...............................................................................................136
Level of Automation .......................................................................136
Earned Business Value (EBV) .........................................................136
Burn-Down Chart ..........................................................................136
Burn-Up Chart ...............................................................................136
Burn Up with Scope Line ...............................................................137
Adding More Agile Metrics .....................................................................139
Case Study: Earned Value Management in the Agile World ....................140
Review Questions ....................................................................................141
Exercise ....................................................................................................141
References ................................................................................................141
Suggested Reading ...................................................................................142
SECTION III LAWS OF PROBABILITY
10
Pattern Extraction Using Histogram .................................................145
Choosing the Number of Intervals ...........................................................148
Square Root Formula ......................................................................148
Alternate Approaches ......................................................................148
Exploratory Iterations .....................................................................148
Process Signature .....................................................................................150
Uniqueness of Histogram Signature ......................................................... 151
Histogram Shapes ....................................................................................152
Mixture ...................................................................................................153
Process Capability Histogram ..................................................................153
Histogram as a Judge ...............................................................................155
From One Point to One Histogram .........................................................156
Case Study: Goal Entitlement ..................................................................156
Appendix 10.1: Creating a Histogram ......................................................158
Interpretation ...........................................................................................159
Review Questions ....................................................................................160
Exercises ..................................................................................................160
References ................................................................................................161
xii ◾ Contents
11 e Law of Large Numbers ................................................................163
Life Is a Random Variable ........................................................................164
Plots of Probability Distribution .....................................................172
Bayes eorem .........................................................................................174
A Clinical Lab Example ..................................................................174
Application of Bayes eorem in Software Development ................176
A Comparison of Application of the Four Distributions and Bayes
eorem ...................................................................................................177
Review Questions ....................................................................................178
Exercises ..................................................................................................179
References ................................................................................................179
Suggested Reading ...................................................................................179
12 Law of Rare Events .............................................................................181
Exponential Distribution .........................................................................182
Poisson Distribution ................................................................................187
A Historic Poisson Analysis: Deaths of Prussian Cavalrymen .........189
Analysis of Module Defects Based on Poisson Distribution ............190
Study of Customer Complaint Arrival Rate Based on Poisson
Distribution ....................................................................................192
Applying Poisson Distribution to Software Maintenance ...............193
Bathtub Curve of Reliability: A Universal Model of Rare Events .............193
Nonhomogeneous Poisson Process (NHPP) ............................................195
Goel–Okumoto (GO-NHPP) Model ......................................................197
Different Applications of Goel–Okumoto (GO) Model ...........................198
Review Questions ....................................................................................201
Exercises ..................................................................................................201
References ................................................................................................202
Suggested Readings .................................................................................202
13 Grand Social Law: e Bell Curve .....................................................205
First-Order Approximation of Variation ..................................................209
Estimation Error ......................................................................................211
Viewing Requirement Volatility ...............................................................212
Risk Measurement ...................................................................................213
Combining Normal Probability Density Functions (PDF): e Law of
Quadrature ..............................................................................................216
An Inverse Problem ..................................................................................219
Process Capability Indices........................................................................221
z Score Calculation ..................................................................................223
Sigma Level: Safety Margin .....................................................................225
Statistical Tests ........................................................................................227
Review Questions ................................................................................... 228
Contents ◾ xiii
Exercises ..................................................................................................229
References ................................................................................................229
Suggested Readings .................................................................................230
14 Law of Compliance: Uniform Distribution ........................................231
Bounded Distribution ..............................................................................233
Random Number Generators ...................................................................233
Shuttle Time ........................................................................................... 234
Parkinson’s Law ...................................................................................... 234
Censored Process .....................................................................................235
Perfect Departure ....................................................................................235
Estimating Calibration Uncertainty with Minimal Information .............235
Review Questions ....................................................................................237
Exercises ..................................................................................................237
References ................................................................................................237
Suggested Readings .................................................................................237
15 Law for Estimation: Triangular Distribution ....................................239
Bell Curve Morphs into a Triangle ..........................................................240
Mental Model for Estimation ..................................................................241
Mean .......................................................................................................242
Median ....................................................................................................243
Other Statistics ........................................................................................245
Skew ........................................................................................................245
ree-Point Schedule Estimation .............................................................247
Beta Option .............................................................................................247
Triangular Risk Estimation .....................................................................248
Parameter Extraction ...............................................................................249
Review Questions ....................................................................................250
Exercises ..................................................................................................250
References ................................................................................................250
16 e Law of Life: Pareto Distribution—80/20 Aphorism ...................253
Structure of Pareto ...................................................................................254
An Example .............................................................................................257
e 80/20 Law: Vital Few and Trivial Many ...........................................257
Generalized Pareto Distribution ............................................................. 260
Duane’s Model .........................................................................................261
Tailing a Body .........................................................................................261
Review Questions ....................................................................................262
Exercises ..................................................................................................262
References ................................................................................................262
xiv ◾ Contents
SECTION IV TAILED DISTRIBUTIONS
17
Software Size Growth: Log-Normal Distribution ..............................267
Log-Normal Processes..............................................................................267
Building a Log-Normal PDF for Software Design Complexity ................270
Working with a Pictorial Approach ..........................................................271
Application of the Log-Normal Model 1 ........................................276
Application of the Log-Normal Model 2 ........................................277
Features Addition in Software Enhancement ...........................................277
A Log-Normal PDF for Change Requests ................................................278
From Pareto to Log-Normal ....................................................................279
Some Properties of Log-Normal Distribution ..........................................279
Case Study—Analysis of Failure Interval ................................................ 280
Review Questions ....................................................................................283
Exercises ................................................................................................. 284
References ............................................................................................... 284
18 Gamma Distribution: Making Use of Minimal Data .........................285
Gamma Curves for Clarification Time Data ...........................................288
Shifting the Gamma PDF ........................................................................290
Generating Clarification Time Scenarios with Gamma PDF Built
from Minimal Data .................................................................................291
Modes .............................................................................................292
Tails ................................................................................................293
Scenario Analysis ............................................................................294
NIST Formula for Gamma Parameter Extraction....................................295
Applying Gamma Distribution to Software Reliability Growth
Modeling .................................................................................................295
Review Questions ....................................................................................297
Exercises ..................................................................................................297
References ................................................................................................298
19 Weibull Distribution: A Tool for Engineers .......................................299
Weibull Curves ........................................................................................301
Parameter Extraction ...............................................................................301
Rules of umb ..............................................................................301
Moments Method ...........................................................................303
MLE ...............................................................................................303
Parameters for Machine Availability Modeling ...............................303
Standard Weibull Curve ......................................................................... 304
ree-Parameter Weibull ........................................................................ 306
Software Reliability Studies .................................................................... 308
Putnam’s Rayleigh Curve for Software Reliability ...................................311
Cost Model ..............................................................................................311
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