Figure 3. Distribution of sample sizes of all eligible 447 articles.
Note: bin from 450 to 500 includes all studies with sample size bigger than 450 but less than 1,000.
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.