Quantification in an argument is seen as a big plus. If someone quotes some statistics, their argument suddenly seems so much more convincing. Yet, statistics is a funny thing. It can be hyped and sensationalised. The same data can be analysed differently to reach conclusions that support your argument. Most people do it mistakenly but there are many cunning minds out there who do it deliberately. People need to protect themselves from this misrepresentation of numbers.
Surprisingly, it is not hard to do. The latest Sense about Science initiative on making sense of statistics gives you quick run through on how can we question these numbers and abstract the true meaning out of them. It is a good example of how being mildly skeptical is generally a good thing.
Some interesting examples that I will quote from the guide are:
- Literary Digest carried out a survey before the 1936 US Presidential Election. It mailed out millions of ballot papers and got two million back; a huge sample, most of which backed the Republican candidate Alf Landon.But the addresses to which they had been sent came from a directory of car owners and from the telephone directory: a biased sample, since in 1936 only the better-off owned cars or had telephones. Franklin D Roosevelt, the Democrat, won the election in a landslide.
- When it was claimed that in the ten most deprived areas in the UK 54% of teenage girls were likely to fall pregnant before the age of 18, it didn’t take long for people to realise this could not be true – it would mean over half of teenage girls from these areas being pregnant. The real figure was 5.4%.
- If you had a room with ten teachers all earning between £20,000 – £30,000, with a If you had a room with ten teachers all earning between £20,000 – £30,000, with a mean salary of £24,900 and a median (mid-point) salary of £25,000 and then someone who earns a million pounds walked into the room, the mean would increase to £114,000 but the median would hardly change. By using the median or mode (most common value) this distortion can be reduced, providing a more representative average salary.
I hope people make use of this guide to help themselves and the society better understand numbers which form a such a significant part of our lives today.