Monday, December 22, 2014

Striking a blow for statistics…

Today’s ruling by the Supreme Court which stymies the Christchurch City Council’s attempts to impose a 67% of “modern code” rule over older building renovation versus the 34% intended by Parliament is a step some way toward perspective around risk, and respect for statistics not politics and unnecessary fear.

No one is dismissive of the horrors of the earthquake. To misunderstand the meaning of the statistical descriptors of such events and to seek solace and backside cover through upping standards to unrealistic levels adds insult to injury while imposing costs to no great benefit.

In respect of the likelihood of earthquake events nothing has changed. The probability of an event of a specified magnitude remains what it was prior to this event and now, after the event.  Because you saw a head come up in a series of coin tosses does not somehow change the probability of heads or tails coming up next flip.

Much the same applies to the ever misinterpreted “return periods” – just because an earthquake with a 100 year return period (say) has just “happened” does not mean:

  • there won’t be one next year;
  • they were “due for one” because the last was 160 years ago;
  • there won’t be one for 160 years; or,
  • any similar grim or glad warning.

It means that over long periods of time events of this magnitude will be observed, on average, once every 100 years.

The hard questions remain. How much do we want to spend to save a life? Is this area the best place to spend our scarce risk management dollar, does what we are planning to spend match the size of the problem we have.

This calls for use of a concept the legal fraternity fancy themselves as experts in – ensuring proportionate responses to events having regard to the evidence.

Statistics refuse to bow to sensationalism, to justify mad regulators in search of zero risk, bureaucrats trying to hide behind ever tighter regulation, journalists seeking easy stories, construction investors and companies seeking demand for risk proof buildings, material suppliers wanting to sell gold plating and much else besides.

If this is baffling – read more statistics. The cost of being baffled is high.

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