Saturday, October 29, 2011
More about lying with statistics
"What have you got against statistics?" a Facebook friend asked after reading the piece, 'Lies, damned lies and statistics.' "Nothing at all", I replied. "I only distrust those who work with statistics." Then I told her a couple of real-life stories.
One of them will bear repeating. Thirteen years ago, I was working on a research project which involved a lot of statistical analysis of data. I consulted two well-known statisticians in Chennai who agreed to do the work for me for a hefty fee. They said that, in their analysis, they would be using three tests (namely, Kruskal-Wallis, Wilcoxon-Mann-Whitney, and Kolmogorov Smirnov) which, they claimed, were "spanking new". A month later, they gave the results. When I checked their calculations at random, I found even their arithmetic incorrect. I had to get the entire data reanalyzed, and it was done with great competence by a young man in
. The young man told me that the three tests used in the analysis were far from new: they had been in use even two decades ago. He showed me the 1977 edition of a book called Non-Parametric Statistical Inference by JD Gibbons, which spoke about the tests. Vijayawada
Lots and lots of such lies pass unnoticed, thanks to what the mathematician John Allen Paulos calls our "mathematical illiteracy". In a lovely little book called Innumeracy he has written, Paulos points out that most people are uncomfortable with basic mathematical principles which makes them poor judges of the numbers they encounter. We accept statistics, both good and bad, with reverence because we don't have a good head for figures.
I never had a good head for figures when I was a student. But a friend of mine whom we called Statistics Srivatsan had a wonderful head. At the slightest provocation, he would launch into a lengthy statistical explanation. Once a language teacher asked him why he was often late. "Often?" Srivatsan asked with a quizzical expression on his face, and continued, "So far in this academic year, you've taken 98 periods, sir. And I've come to 82 of them on time, which is 8.3 per cent higher than the class average of …"
Once Srivatsan quizzed me with a statistic. "Do you know, Ramanujam, that, in this world, every ten seconds, a woman gives birth to a child? What do you think about it?" "Think about it!" I burst out. "Who is that irresponsible woman? We must tell her to stop it at once." Srivatsan fixed me with a gaze of cold hardness that would have frozen an Eskimo.
I wonder where Statistics Srivatsan is now. Wherever he is, he must be a statistician; I can't picture him as anything else. And he must be lying with statistics as impressively as he did when the teacher asked him whey he was often late.