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 slope of the continuous lines is: –1.01±0.03 (squares) and –1.05±0.02 (circles). The standard deviation is smaller than the symbol. For details, see text.
