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Stream and mountains

The Dangers of Believing Everything you Read

“The Numbers don’t lie… or do they?”

An opinion piece written by Gian Ellis-Gannell

-Editor in Chief of The Mary Word

Recently in the media we have seen a growth in the number of children developing measles, mumps and rubella: diseases all preventable through the popular use of the MMR vaccine. Despite the vaccines common use however, a spike in numbers can be contributed to the frankly dangerous “Anti-Vax” movement. It has been identified by the World Health Organization as one of the top ten global health threats of 2019, and unfortunately may have been largely preventable; if only someone explained to those who rigorously defend their cold hard ‘facts’, that correlation does not equal causation.

Identified as post hoc ergo propter hoc, or ‘The Post Hoc Fallacy’, this is the logical fallacy that states that "Since event Y followed event X, event Y must have been caused by event X.” (or in Latin: “after this, therefore because of this"). The Post Hoc Fallacy is an identified, flawed method of thinking, in which the possibility of a coincidence is ruled out, and a connection is made between two likely unrelated events (or as is common today, statistics).

To dismantle the main argument of the ‘Anti-Vax’ movement which is destroying herd immunity, we can state under the basis that the fallacy leads to false thinking, that just because immunisation rates increase at the same time as autism diagnosis rates, there is no logical reason to state the two are connected. Methods of diagnosing Autism have advanced, just like humans, and children who could previously only be diagnosed at age 7, can now be diagnosed at 9 months, meaning doctors have more opportunities to assist our youth. Immunisation rates have increased rather as widespread education does, as people are more aware of the dangers of being unvaccinated.

This is a much more logical way of viewing the situation, however it is one that not every person immediately notices. Perhaps through the strength of media, many are brainwashed into thinking that in the case of vaccinations, correlation does equal causation, but consider this:

In the 1970’s in Canada, margarine use as a lower-fat alternative to butter increased by 17%. In that same time period, divorce rates also rose by 17%. Under the Post Hoc Fallacy, does that mean that margarine use causes divorce? Is my dedicated margarine-using parents’ marriage destined to fail?

In statistics, many mathematical tests calculate correlations between variables, and when two variables are found to be ‘correlated’, it can be tempting to assume that this shows that one variable causes the other when it suits our own agenda. However, this method of thinking can lead to hilariously and obviously flawed data. Take this surprisingly legitimate graph taken out of public data and made by Tyler Vigen - A correlation of 87% would suggest a strong likelihood the two events are linked.

And surprisingly,

Now - these can get more and more ridiculous, but one gets the point. You must ask however, how could this correlation be possible? These are not the popular ‘alternative facts’ that circulate the internet, they are true numbers. They are real, but they are also completely coincidental, and believing them can be extremely dangerous as we see from the anti-vaccination movement. Then again, the numbers don’t lie- or do they?


  • Australian Bureau of Statistics (2019). Statistical Language - Correlation and Causation. [online] Available at: [Accessed 27 Feb. 2019]

  • Fast Company. (2014). Correlation Isn’t Causation. [online] Available at: [Accessed 27 Feb. 2019].

  • HCF. (2019). The anti-vaccination movement: myths vs facts | HCF. [online] Available at: [Accessed 1 Mar. 2019].

  • Logically Fallacious (2019). Questionable Cause. [online] Available at: [Accessed 2 Mar. 2019]

  • Science Based Medicine .org. (2019). Evidence in Medicine: Correlation and Causation. [online] Available at: [Accessed 1 Mar. 2019]

  • Weightology. (2019). Thinking Better, Part 3: Non Causa Pro Causa. [online] Weightology. Available at: [Accessed 1 Mar. 2019].


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