Statistics for Maintenance Modelling: Continuous Lifetime Distributions 2

# Example of Fitting the Pareto Distribution to Software Failures During Testing¤

The table gives the interval between successive software failures recorded during factory testing.

Pareto models have often been fitted to this type of data as the time to failure is expected to increase as more errors are found - and software does not wear out like mechanical items. Fitting a Pareto distribution with = 0.5 and = 0.29 gives:

Time range (hours) | Number of failures
--- | ---
0-1 | 99
01-Feb | 54
02-Mar | 15
03-Apr | 7
04-May | 0
05-Jun | 1
06-Jul | 2
Total | 178

This data comes from MUSA, J .D. (1979) Validity of execution-time theory of software reliability. IEEE Transactions on Reliability, 28(3) (August), 18 -191.