Conversion MTBF to R(t)
Number of test specimen n	-
Test duration T	hr
Number of failures r	-
MTBF = n·T/r	hr
Failure rate λ = 1/MTBF	%
R(MTBF) = exp(-λt)	-
R(0.5MTBF)	-
t(R=0.95)/MTBF	-
Mean Time Between Failure (MTBF) of Hard Disk Drives
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