"Any claim coming from an observational study is most likely to be wrong"

This article from the journal "Significance"

Deming, data and observational studies
Author: S. Stanley Young, Alan Karr
Published: Aug 25, 2011 - From issue: Volume 8 Issue 3 (September 2011)
Doi: 10.1111/j.1740-9713.2011.00506.x

suggests a process control-based solution for improving the success rate of observational studies.

To better appreciate the problem of multiple testing, they suggest visiting Jery Dallal's simulation web page, which illustrates what happens when one carries out "100 Independent 0.05 Level Tests For An Effect Where None Is Present".