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Between 1997 and 2007, the rate of autism and organic food sales has risen at the same rate. Obviously, this chart goes to prove that autism and eating organic foods are related to each other and you should avoid organics all together, right? Wrong. This chart is one of the best examples I’ve ever seen detailing how correlation and causation can have absolutely nothing to do with each other. In fact, in many cases, correlation and causation have nothing to do with each other – but what exactly does that mean?

In Latin, the phrase generally used is “cum hoc ergo propter hoc” which translates more literally to “With this therefore because of this.” The opposite, however, is true. Causation proves correlation, but not the other way around.

If a correlation is established, how can you determine causation? Are they caused by the same thing? Does one cause the other? Are they completely unrelated? In order for one event to cause another, they must be related. In other words, there must be some real mechanism connecting the two events (assuming the correlation isn’t completely coincidental). Here, the cause and effect mechanism must comply with the known laws of nature – this (at least) gives us somewhere to start.

The simple question might be “why do such unlikely coincidences occur in our lives?” But the real question is how to define the unlikely. You know that a situation is uncommon just from experience. But even the concept of “uncommon” assumes that like events in the category are common. How do we identify the other events to which we can compare this coincidence? If you can identify other events as likely, then you can calculate the mathematical probability of this particular event as exceptional.

We are exposed to possible events all the time: some of them probable, but many of them highly improbable. Each rare event—by itself—is unlikely. But by the mere act of living, we constantly draw cards out of decks. Because something must happen when a card is drawn, so to speak, the highly improbable does appear from time to time.

To this end, we suggest 20 concepts that should be part of the education of civil servants, politicians, policy advisers and journalists — and anyone else who may have to interact with science or scientists. Politicians with a healthy scepticism of scientific advocates might simply prefer to arm themselves with this critical set of knowledge. We are not so naive as to believe that improved policy decisions will automatically follow. We are fully aware that scientific judgement itself is value-laden, and that bias and context are integral to how data are collected and interpreted. What we offer is a simple list of ideas that could help decision-makers to parse how evidence can contribute to a decision, and potentially to avoid undue influence by those with vested interests. The harder part — the social acceptability of different policies — remains in the hands of politicians and the broader political process. Of course, others will have slightly different lists. Our point is that a wider understanding of these 20 concepts by society would be a marked step forward.