262 ◾ Simple Statistical Methods for Software Engineering
management, project management, software development and problem solving. It
is also used in reliability modelling.
Review Questions
1. What is the meaning of 80/20 law?
2. What is the Pareto principle?
3. Why is Pareto distribution called a fat tailed distribution?
4. Which distribution has the fattest tail: Gaussian, exponential, or Pareto?
5. Give three examples of Pareto laws.
Exercises
1. Calculate the mean value of Pareto distribution if mode = 7 and shape = 4.
2. Calculate the median value for the previous case.
3. Assume the defect density distribution of a certain application follows Gaus-
sian tail. If the threshold of defect density is six units (relative value), what is
the reliability of the application? (Clue: make use of the calculation shown in
Box 16.2: A Story of Tails.)
4. Assume the defect density distribution of a certain application follows expo-
nential tail. If the threshold of defect density is six units (relative value), what
is the reliability of the application? (Clue: make use of the calculation shown
in Box 16.2: A Story of Tails.)
5. Assume the defect density distribution of a certain application follows Pareto
tail. If the threshold of defect density is six units (relative value), what is the
reliability of the application? (Clue: make use of the calculation shown in Box
16.2: A Story of Tails.)
References
1. T. Illes-Seifert and B. Paech, e Vital Few and Trivial Many: An Empirical Analysis
of the Pareto Distribution of Defects. Software Engineering, Kaiserslautern, Germany,
2009, pp. 151–164.
2. T. J. Ostrand and E. J. Weyuker, e distribution of faults in a large industrial soft-
ware system, In: Proceedings of the 2002 ACM SIGSOFT International Symposium on
Software Testing and Analysis (ISSTA), ACM Press, Roma, Italy, 2002, pp. 55–64.
3. A. Murgia, G. Concas, S. Pinna, R. Tonelli and I. Turnu, Empirical Study of Software
Quality Evolution in Open Source Projects Using Agile Practices.
4. G. L. Simmons and T. S. Dillon, Towards an ontology for open source software devel-
opment, International Federation for Information Processing, 203, 65–75, 2006.