== Unclear article == 

 Please define the word event that is used in the first phrase. 

 The 3rd paragraph associates common mode failure with redundancy. The association is however too weak to put at this place. In addition, the association is not made sufficiently clear. The association seems to be that common mode failure is about statistically dependent events, whereas redundancy is related to statistically independent events. In the following example of a RAID system, the differences are made clear; it explains why redundancy can fail due to common mode failures. To make a long story short, redundancy should be put in a seperate section, preferrably at the end of the article.