Normally when somebody finds an association in an epidemiological study people are quick to point out that it doesn't prove causality, that there are problems of missing co-founders, that it is at ...
As I understand it, matching is one way to identify causality in observational studies. By matching observations that are "similar" and comparing ones that did or did not receive treatment, you can ...
Imagine that you are planning a study about risk behaviours among HIV positive injecting drug users. All the individuals included in the sample are injecting drugs and all are HIV positive. The main ...