Figure 1.
Diagrammatic summary of the sample size (sampling procedure) for each region and city administration based on the stratification and proportion of their health care work force.
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.