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.
Closed circles indicate the number of bases in each MI value range (0.5). The vertical dotted line indicates the mean value (2.54).
