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.
Details are given as percentages for correct answers, both for the overall group (light grey bars) and divided into each age group (dark grey bars). *** Highly significant association, P < 0.005; ** very significant association, P < 0.01.
