Hair Breakage 278 Weibull analysis and relative humidity: With the above disclaimer in place, it becomes possible to evaluate and examine Weibull results for Caucasian hair tested under differing humidity conditions. Results are given in Table 9 and Figure 18. All data points are based on 75 individual fibers. Table 9. Weibull parameters for Caucasian hair as a function of repeated stress and relative humidity Stress Range 20% RH 60% RH 90% RH 0.006‑0.007 g/μm2 - - - - 186,000 0.97 0.007‑0.008 g/μm2 - - - - 48,000 0.69 0.008‑0.009 g/μm2 - - - - 8,350 1.08 0.009‑0.010 g/μm2 - - 158,000 0.83 2,550 1.09 0.010‑0.011 g/μm2 - - 35,800 0.86 1,100 1.57 0.011‑0.012 g/μm2 - - 18,100 0.79 815 1.19 0.012‑0.013 g/μm2 116,000 0.61 6,030 0.89 548 1.09 0.013‑0.014 g/μm2 36,700 0.69 1,970 1.06 - - 0.014‑0.015 g/μm2 10,300 0.63 1,260 1.07 - - 0.015‑0.016 g/μm2 4,820 0.80 0.016‑0.017 g/μm2 2,820 0.59 A graph of characteristic lifetime versus stress again reflects the sizable influence of the relative humidity on the tendency for fiber breakage. Moreover, there is also the suggestion of different breakage mechanisms. Experiments at low humidity apparently yield lower shape parameters, with this tendency seemingly being progressively alleviated as the humidity rises. Shape parameter results can potentially be skewed quite considerably by the presence of apparent outliers and so again it is prudent to focus on trends rather than any individual point. Shape parameter results from these experiments are summarized in Figure 19. The presence of progressively lower shape parameters with decreasing stress magnitude is in-line with fatigue theory. Moreover, the aforementioned trends appear evident. This said, it appears