of Reliability Analysis: The more reliable a product is, the harder it
is to get the failure data needed to "prove" it is reliable!
There are two closely related problems that are typical with reliability
data and not common with most other forms of statistical data. These are:
These problems cause considerable practical difficulty when planning reliability
assessment tests and analyzing failure data. Some solutions are discussed
in the next two sections. Typically, the solutions involve making additional
assumptions and using complicated models.
Censoring (when the observation period ends, not
all units have failed - some are survivors)
Lack of Failures (if there is too much censoring,
even though a large number of units may be under observation, the information
in the data is limited due to the lack of actual failures)