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.
Pólya urn demonstrations of (a) the Matthew effect and (b) the compensation effect. Starting with an urn that contains a white marble and a black marble, in each trial the drawn marble is replaced with two or three marbles of the same color, depending on the desired effect. The figures show the development of the proportion of marbles for 50 independent urns.
