Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The distribution of BC levels are shown for the two measuring phases of the challenge. The vertical axis shows the density, i.e. the normalised frequency of the various BC levels measured, so that the area under the plot is 1. The inset shows the same plot but with a logarithmic vertical axis, to emphasize the tail of the distribution.
