Fig. 1.
Schematic diagram of the survey instrument. Compulsory questions that lead participants to be skipped to particular sections within the survey, together with their possible answers are shown in boxes
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.