  Jammed packings of granular materials differ from systems normally described
by statistical mechanics in that they are athermal. In recent years a
statistical mechanics of static granular media has emerged where the
thermodynamic temperature is replaced by a configurational temperature X which
describes how the number of mechanically stable configurations depends on the
volume. Four different methods have been suggested to measure X. Three of them
are computed from properties of the Voronoi volume distribution, the fourth
takes into account the contact number and the global volume fraction. This
paper answers two questions using experimental binary disc packings: First we
test if the four methods to measure compactivity provide identical results when
applied to the same dataset. We find that only two of the methods agree
quantitatively. Secondly, we test if X is indeed an intensive variable; this
becomes true only for samples larger than roughly 200 particles. This result is
shown to be due to recently found correlations between the particle volumes
[Zhao et al., Europhys. Lett., 2012, 97, 34004].
