Friday, 29 November 2013
Boris Johnson has given us an example of how to distort the truth with statistics which should enter the text books. In his speech this week to the right wing Centre for Policy Studies Johnson doesn't actually lie: he presents absolute truth, but in such a way as to give a hugely twisted impression.
Johnson points out that 16% of "our species", as he calls us, have an IQ of less than 85 whereas only 2% have an IQ of more that 130. Absolutely correct.
For those unfamiliar with the background, many natural phenomena display a Gaussian, or Normal, distribution, which , in graphical terms, produces a bell-shaped curve with the vast majority in the middle and few at each of the extremes. This can be validated by actually measuring observable features such as, for example, human height.
Most educational psychologists presume that human intelligence is similarly distributed, but, since intelligence is hard to measure (and perhaps even harder to define) this is impossible to prove. However, intelligence test are constructed so as to produce a Gaussian distribution, with both a median and modal score of 100, and questions in IQ tests are deliberately chosen to produce this. Questions which generate results which do not fit this "normal" distribution are rejected.
Johnson's distortion is to appear to balance the 16% with an IQ below 85 against the 2% with IQs above 130, thus giving the impression that the "gifted" 2% have to carry the "subnormal " 16%. But note that the 2% are 30 points above the norm whilst the burdensome 16%, with IQs below 85, are only 15 points below the norm.
In actual fact, there will be precisely 2% of the population with IQs below 70 who will exactly balance the 2% with IQs above 130, and 16% with IQs above 115 to balance those below 85.
What ever the figures, who owes what to whom by no means follows. IQ may affect propensity to pass exams, but it doesn't measure hard work, ambition, care, consideration, empathy, sense of adventure, willingness to take risks, or how good a partner, parent (or teacher or nurse) you're likely to be. In the hackneyed phrase, "It takes all sorts to make the world," and in a modern democracy we all merit equal respect and consideration as citizens.