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 background-corrected integral counting rate R (in units of counts per second) for each of 195 SRM 4321d ampoules plotted versus ampoule number (filling order) as measured in a NaI(Tl) well counter. The dashed lines show the mean ± 2s interval, where s is the standard deviation of the distribution for the n = 223 measurements. Twenty-eight ampoules were measured in duplicate, with a 0.16 % average relative difference.
