Monday, January 3, 2011

How to read statistics

Statistics can be interpreted in many different ways: just notice how political parties (and allied mass media) read poll results to realise that statistics, without any context or explanation, can be easily misinterpreted. Churchill used to say that he only believed in statistics that he doctored himself. John Allen Paulos’ book Innumeracy: Mathematical Illiteracy and its Consequences is a very interesting reading material to better understand statistics. This book shows that we know absolutely nothing about mathematical culture so it is very easy to fool us if we cannot even understand a statistic.A good proof of it is the recent reporting of sexual harassment by two Swedish girls against WikiLeaks founder Julian Assange. Some mass media, in an attempt to provide some context to this piece of news, offered the following fact: Sweden is the country with the highest rape rate in Europe. But if we look up the sourcebook of this information, we realise that it should be properly interpreted: according to this survey, Sweden is the country with the highest reported rape rate (53 rapes per 100,000 population) in Europe. Therefore, these figures do not show the actual number of rape offences committed but the high level of confidence of Swedish people in their justice and their low tolerance on such abuses. At least, these 53 reported rapes per 100,000 population in Sweden contrast with the 2 cases in Turkey, 3 in Albania, 2 in Greece or 5 in Spain. Is it a problem in Sweden or in the rest of countries?

Sources:
  1. Churchill's quote: http://en.wikiquote.org/Churchill
  2. Innumeracy: Mathematical Illiteracy and its Consequences: http://en.wikipedia.org/wiki/Innumeracy_(book)
  3. European Sourcebook of Crime and Criminal Justice Statistics 2010 (page 46): http://www.europeansourcebook.org/ob285_full.pdf

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