Causality: The relating of the reasons to the effects they produce. Several investigations in medicine seek to establish the causal relations between the events, for instance, which receiving the treatment A causes patients to live longer than taking the treatment B. In common the strongest claims to have established causality come from the data collected together in the experimental studies. Relationships established in the observational studies might be very suggestive of the causal link but are always open to the alternative explanations and results.