Figure 9 shows survival probability plots as a function of the applied stress, which were
calculated from the data in Table II. The results appear logical, and refl ect how application
of higher stresses decreases the survival probability. However, the usefulness of these
plots becomes clear in attempting to model the infl uence of different experimental variables.
For example, Figure 5 convincingly reminds us that a reduction in the fatiguing
force can dramatically increase the number of cycles before breakage occurs. Now it becomes
possible to express this occurrence in terms of the probability of fi ber breakage. An
example is shown in Table III, in which differences in the applied stress are accounted for
in terms of a decreasing fatiguing force applied to fi bers of common dimension. Thus, it
is predicted that decreasing the fatiguing force on a 70-μm fi ber from 52.0 g to 36.6 g
results in the probability of fi bers surviving 5,000 cycles, increasing from virtually zero
to almost 100%. This very clearly illustrates the benefi ts of lubricating hair treatments