Archives For conditional probability

We are hectored on an almost daily basis as to the imminent threat of islamic extremism and how we must respond firmly to this real and present danger. Indeed we have proceeded far enough along the escalation of response ladder that this, presumably existential threat, is now being used to justify talk of internment without trial. So what is the probability that if you were murdered, the murderer would be an immigrant terrorist?

In NSW in 2014 there were 86 homicides, of these 1 was directly related to the act of a islamist terrorist (1). So there’s a 1 in 86 chance that in that year if you were murdered it was at the hands of a mentally disturbed asylum seeker (2). Hmm sounds risky, but is it? Well not really, there was approximately 2.5 million people in NSW in 2014 so the likelihood of being murdered (in that year) is in the first instance 3.44e-5. If we multiply this by the likelihood that it was at the hands of a `terrorist’ then we end up with 4e-7 or 4 chances in 10 million. If we consider subsequent and prior years where nothing happened that likelihood becomes even smaller.

Yet based on this 4 in 10 million chance for one year the NSW government intends to build a super-max 2 prison in NSW, and fill it with ‘terrorists’ while the Federal government enacts more anti-terrorism laws that take us down the road to the surveillance state, if we’re not already there yet. The glaring difference between the perception of risk and the actuality is one that our political class seem oblivious to (3).

Notes

1. One death during the Lindt chocolate siege that could be directly attributed to the `terrorist’.

2. Sought and granted in 2001 by the Liberal National Party government.

3. An action that also ignores the role of prisons in converting inmates to Islam as a route to recruiting their criminal, anti-social and violent sub-populations in the service of Sunni extremists.