It is human nature to try to explain what we observe occurring around us, a process that people engaged in long before physical, biological or social sciences were established as disciplines. The difference between ëcommon senseí explanations and scientific ones lies in the way the two originate. Everyday observations are haphazard, careless and not systematic, whereas those carried out by scientists endeavour to be specific, objective, well focused and systematic, to the extent that they could be replicated by someone else. While there are few true guarantees, the more systematic and organised the studies we conduct, the more likely they will produce valid explanations that can be used to support decisions.