Specifies procedures to verify the assumption of a constant failure rate or constant failure intensity as defined in IEC 60050(191). These procedures are applicable whenever it is necessary to verify these assumptions. This may be due to a requirement or for the purpose of assessing the behaviour in time of the failure rate or the failure intensity. The major technical changes with respect to the previous edition concern the inclusion of corrected formulae for tests previously included in a corrigendum, and the addition of new methods for the analysis of multiple items.