Here are some tutorials that will help with understanding some of the aspects of these studies:

What are "Statistical Errors" and what are "95% Confidence Level" limits?

What are the systematic errors in medical studies?

How are medical studies done, and how is their outcome reported.

Peer Review

Why do we focus on "peer reviewed" journal articles?

What does "risk" mean?

Explains the role of statistics in everyday life, with simple examples.