Friday, March 22, 2013

Smoking rates: even the 'good guys' shouldn't be trusted

The Guardian reports today that the number of children under 16 (more precisely aged 11-15) taking up smoking has has risen by 50,000 in a single year.  This is a slightly irritating headline simply because the number is without context, but the sub-headline is more helpful: from 157,000 to 207,000, which is quite dramatic: a 32% increase.

First obvious question - is this statistically significant? Well, let's have a look at the research quoted by the Guardian, which comes from Cancer Research UK.  Their Figure 6.10 immediately arouses suspicion.  There does appear to be an uptick in the figures from 2010 to 2011, but they remain below the 2009 figure!  The overall trend in the numbers over the past 10 years is clearly downwards.  So either we believe that the number of children taking up smoking fell and then rose dramatically in consecutive years, or else we might just be witnessing a bit of noise in our data.