Table 1

Process reliability levels5

DefinitionDefect rate
Chaotic or undefined reliability-focused processesMore than two defects out of 10 (less than 80% success)
10−1One or two failures out of 10 (80% to 90% success)
10−2Five failures or fewer out of 100 opportunities (95% success)
10−3Five failures or fewer out of 1000 opportunities (99.5% success)
  • In this paper, we focus not on what would be the best unit of measuring reliability but on concepts, practices and methods which determine and/or influence reliability. Nonetheless, it is important to say that precise measurement of reliability is crucial for actually improving reliability over the course of time.