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.
Examples of directed acyclic graphs containing a “collider” (the common effect of two or more causes).33 Conditioning on observing a collider alters the apparent covariation among the causes; for example, two independent causes that are uncorrelated when all observations are considered can appear to be negatively correlated when only observations containing the collider are considered.
