Reliability and Effective Failure Rate of "n" Active Redundant Units, with "m" Required for Success, and "n-m" Cold Standby Units

This tool calculates the reliability function and effective failure rate for "m of n" units, where n-m units are "cold standby" spares. It assumes:

all units are identical

active on-line units have a constant failure rate (i.e., fail according to the exponential distribution)

non-operating standby units have a failure rate of zero

The tool also calculates system mean time to failure (MTTF) for the case where the system is operated without renewal. It is similar to
this tool, but is more comprehensive in that it handles an arbitrary number of cold standby spares, computes the reliability,
and uses numerical integration to compute the effective mean time between failure (MTBF), sometimes referred to as the mean time between critical failure (MTBCF).
For additional details, click here.