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 error function, ERF (solid line) represents the cumulative density function fitted to the data. The mean and standard deviation obtained from the ERF define the probability density function, corresponding to a normal distribution (PDF, dashed line).
