I am wondering why certain components in the NPRD 1995 database have a much lower failure rate compared to the NPRD 2011 database.For example in the 1995 library the failure rate (Per million hours) for a screw with a hex head was 0.1140 whereas for the same component in the 2011 library has a lowest failure rate of 2.7362. This is causing the MTBF figure to be very low within the my study and no one seems to know which value to use. For my analysis should I use the 2011 database over the 1995 database?
