
118 n Designing Complex Systems
an exponential distribution, particularly when we consider the nonlinear interval
scale.
Both MTBF and MTTR are functions of three parameters, λ, ∆, and s
1
, and
before we attempt to obtain useful approximate expressions for these functions, we
need to consider the relationship between failures and the spike (introduced in sec-
tion 7.5.1). Let us introduce two parameters, similar to MTBF and MTTR, for the
spike, mean time between strikes (MTBS), and mean time in strike (MTIS). ese
two parameters are functions of λ and ∆, but, of course, do not depend on s
1
. It is
then straightforward to see that the followin