What do you think?
Rate this book


Quando foi publicado pela primeira vez, em 1954, o livro de Darrell Huff foi saudado como pioneiro em conjugar linguagem simples e ilustrações para tratar de um tema polêmico e controverso: o mau uso da estatística para maquiar dados e abalizar opiniões. Hoje, em tempos de internet e big data, o livro continua genuinamente subversivo e ainda mais relevante. Qual é, afinal, o grau de confiança que devemos depositar nas análises estatísticas?
Segundo Huff, vale ter sempre um pé atrás. Amostras enviesadas, gráficos dúbios, listagens incompletas: item por item o autor apresenta os vilões da interpretação de dados. Em um capítulo, ele aponta como os gráficos estatísticos, mesmo matematicamente corretos, podem não representar em nada a realidade. Em outro, vemos que uma mesma projeção pode mostrar um futuro positivo ou alarmante, dependendo da amplitude de dados que ela cobre. O livro termina com um brilhante passo a passo para o leitor aprender a diferenciar informação de enrolação.
Escrito com humor e repleto de advertências tão atemporais quanto a ciência matemática, Como mentir com estatística é uma leitura agradável e absolutamente acessível. Indispensável para quem se vê bombardeado diariamente, seja pela mídia ou pela timeline do Facebook, por infográficos e estatísticas que se pretendem verdades incontestáveis.
“Uma exploração hilária das mentiras da matemática.”The New York Times
“Peça por peça, Huff desmonta o modo como os marqueteiros usam estatísticas, tabelas e gráficos para apresentar números que confundem e enganam o público.”The Wall Street Journal
144 pages, Kindle Edition
First published January 1, 1954
The next time you learn from your reading that the average man (you hear a good deal about him these days, most of it faintly improbable) brushes his teeth 1.02 times a day - a figure I have just made up, but it may be as good as anyone else's - ask yourself a question. How can anyone have found out such a thing? Is a woman who has read countless advertisements that non-brushers are social offenders going to confess to a stranger that she does not brush her teeth regularly? The statistic may have meaning to one who wants to know only what people say about tooth-brushing but it does not tell a great deal about the frequency with which bristle is applied to incisor.
A good deal of the sillier criticism of Dr Alfred Kinsey's well-known (if hardly well-read) report comes from taking normal to be equivalent to good, right, desirable. Dr Kinsey was accused of corrupting youth by giving them ideas and particularly by calling all sorts of popular but unapproved sexual practices normal. But he simply said that he found these activities to be usual, which is what normal means, and he did not stamp them with any seal of approval. Whether they were naughty or not did not come within what Dr Kinsey considered to be his province. So he ran up against something that has plagued many another observer: It is dangerous to mention any subject having high emotional content without hastily saying whether you are for or against it.
There are often many ways of expressing any figure. You can, for instance, express exactly the same fact by calling it a one percent return on sales, a fifteen percent return on investment, a ten million dollar profit, an increase in profits of forty percent (compared with the 1965-9 average), or a decrease of sixty percent from last year. The method is to choose the one that sounds best for the purpose at hand and trust the few who read it will recognise how imperfectly it reflects the situation.
"The secret language of statistics, so appealing in a fact-minded culture, is employed to sensationalize, inflate, confuse, and oversimplify. Statistical methods and statistical terms are necessary in reporting the mass data of social and economic trends, business conditions, 'opinion polls', the census. But without writers who use the words with honesty and understanding and readers who know what they mean, the result can only be semantic nonsense… This book is a sort of primer in ways to use statistics to deceive. It may seem altogether too much like a manual for swindlers. Perhaps I can justify it in the manner of the retired burglar whose published reminiscences amounted to a graduate course in how to pick a lock and muffle a footfall: The crooks already know these tricks; honest men must learn them in self-defense." (10-11)I never cared much for statistics; I slid through Methods & Statistics 1, 2, and 3 relatively untouched, until the first time I did my own research and had to analyze the data I had so diligently collected. That was the point at which statistical analyses became meaningful to me—I had a theory and I was looking to see whether there was any evidence for it. The data itself means nothing, of course. Numbers do not mean anything on their own. What you do with the numbers, how you expose (non-)relationships between them, is when things get interesting. And tricky—as this little book sets out to show.