  The first plastic event occurring in discrete intermittent plasticity, as for
example a pop-in seen in nano-indentation, is evaluated with extreme value
statistics. It is found that when the same deformation is repeated many times,
the average of the stress at this first event is related to the deforming
volume via an exponentially truncated power-law. The present work demonstrates
this trend and the expected Weibull fluctuation around it. The statistical
formalism is shown to apply to the nano-indentation data of Morris {\em et al},
Phys. Rev. Lett. 106, 165502 (2011), as well as to dislocation dynamics
simulations, which suggests a general phenomenon is at play. The truncated
power law is found to uniquely determine an underlying critical stress master
probability density function in terms of the Lambert-W function and the density
of discrete plastic events available to the crystal. Thus the developed
procedure allows for a quantitative characterization of a bulk material's
initial microstructure via a deformation experiment that probes discrete
intermittent plasticity.
