ISBN : 978-81-963532-2-3 (E-Book) . Fig.27.1:Stepfunction modelofreliabilitygrowth Littlewood and Verall’s Model -This model allows for negative reliability growth to reflect thefact that when a repair is carried out, it may introduce additional errors. It also models the factthat as errors are repaired, the average improvement in reliability per repair decreases (Fig. 27.2).It treat’s an error’s contribution to reliability improvement to be an independent random variablehaving Gamma distribution. This distribution models the fact that error corrections with largecontributions to reliability growth are removed first. This represents diminishing return as testcontinues. Fig.27.2:Random-stepfunctionmodelofreliabilitygrowth StatisticalTesting Statistical testing is a testing process whose objective is to determine the reliability of softwareproducts rather than discovering errors. Test cases are designed for statistical testing with anentirelydifferent objectivethan thoseof conventional testing. 114 Software Engineering Keerthana P, Manasa KN, Ganga D Bengal
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