<\/p>\n
I recently finished reading a book that I started reading over six months ago when I bought it up from a remaindered bin at 70% off.<\/p>\n
The book is titled Reckoning With Risk<\/a>: Learning to Live with Uncertainty<\/em>, by Gerd Gigerenzer. <\/p>\n With a title like that, the publishers have made it sound like a self-help book, but it is not.<\/p>\n That’s not why I picked it up. Based on its blurb, I thought it might be a book describing the psychological hoops humans will jump through to convince themselves that they are in control in an uncertain world, but it is not.<\/p>\n Instead, it is a book similar to Innumeracy<\/a>: Mathematical Illiteracy and its Consequences<\/em>, by John Allen Paulos. It argues that misunderstandings about the assessment of risk affect serious decisions made in people’s lives.<\/p>\n He doesn’t spend much time on the inability for people to estimate the chance of low-risk activities (and use it, for example, to determine whether to wear a seat-belt.)<\/p>\n Instead, he focusses on the way the presenting the same information to people in a “natural frequencies” format is preferable to a “conditional probabilities” format. He gives a real-life example, where he was required to get an AIDS test for a U.S. green-card.<\/p>\n About 0.01 percent of men with no known risk behaviour are infected with HIV (base rate). If such a man has the virus, there is a 99.9 percent chance that the test result with be positive (sensitivity). If a man is not infected, there is a 99.99 percent chance that the test result will be negative (specificity).<\/p><\/blockquote>\n The question he asks is “If I test positive in this HIV test, what is the chance that I will actually have HIV?”<\/p>\n Although all the information you need to answer that question is in the above paragraph, it is easier to reason about it if you present the same information in a different format.<\/p>\n Imagine 10,000 men who are not in any known risk category. One is infected (base rate) and will test positive with practical certainty (sensitivity). On the 9,999 men who are not infected, another one will also test positive (false positive rate). So we can expect two men will test positive.<\/p><\/blockquote>\n From here, it is clear that if someone (in a low risk group) tests positive, there is only a 50-50 chance that they have the disease.<\/p>\n This simple idea of presenting the statistics in a different format to aid understanding is the key idea in the book. In fact, it is almost the only idea. I originally considered creating a tongue-in-cheek review of the book that went along the lines of:<\/p>\n In Chapter One, Gigerenzer introduces the idea that natural frequencies are a better way of presenting statistics. In Chapter Two, Gigerenzer argues that natural frequencies are a better way of presenting statistics. In Chapter Three, Gigerenzer gets into his stride, arguing that natural frequencies are a better way of presenting statistics. (etc.) Chapter Fourteen summarises the arguments in the previous chapters by suggesting that, perhaps, there is a better way of presenting statistics, called natural frequencies.<\/p>\n That’s why it took me six months to read. It was a little dull and repetitive.<\/p>\n I decided not to write the cynical review; it seemed too petty, and it wasn’t really fair. The author did introduce some other concepts too, and one of the reasons the work seemed so repetitive is that he provided copious evidence of experiments showing how people had completely misunderstood various statistics, and how simply re-presenting the same information helped people’s cognition immensely.<\/p>\n Examples included: Breast screening, AIDS counselling, Wife Battering, DNA fingerprinting, releasing violent people from jail, and less important examples, like the infamous Monty Hall puzzle.<\/p>\n What made me change my mind, and write this review? The case of Andrew Stimpson.<\/p>\n Andrew Stimpson has made news recently because of his miraculous “cure” from AIDS. He was tested positive for HIV several years ago, considered suicide, took no medication, partook in “dangerous” practices (e.g. unprotected sex with his HIV-positive boyfriend), and yet has recently tested negative for HIV.<\/p>\n The media hailed this as a miracle cure from AIDS, quoting the original diagnosticians as saying there was no room for error in the tests.<\/p>\n Bullshit!<\/p>\n I do not know whether Stimpson was properly informed of the chance that there could be a false positive. Gigerenzer described an experiment where a majority of German AIDS counsellors , when directly asked by a researcher pretending to be a patient, “incorrectly assured the client that false positives never occurred”. So, there is a good chance that Stimpson was not informed of the chance. <\/p>\n Even if he was told, there is a good chance, according to Gigerenzer, that Stimpson would not have been able to understand the risks (unless, of course, they had been presented in “natural frequencies”!)<\/p>\n Either way, it seems likely to me that an HIV-free Stimpson walked out of that clinic with the firm belief that he was HIV-positive, no two ways about it. Had he committed suicide, or subsequently contracted HIV through discarding safe practices, the situation would have been tragic.<\/p>\n According to the media, the clinic initially maintained their position that both tests were accurate.<\/p>\n Then doubt<\/a> was raised<\/a> about the second (negative) test, and Stimpson was urged to get another test, debating whether it was the appropriate test.<\/p>\n I would equally question the results of the first<\/em> test. I believe Gigerenzer’s figures are more illustrative than definitive, but he rates an HIV-positive result amongst gay men<\/em> (who have a base-rate of HIV-infection around 1.5% – I assume Germany and the UK have similar base-rates) as meaning there is “only” a 1 in 151 chance that you do not have the disease – bad news, for sure, but it leaves a big gap from the “miracle” that the papers describe.<\/p>\n The medical and the media professions would do well to reconsider how they present the information to their patients and their readers. Perhaps Gigerenzer was right in ramming the same point home several times in his book.<\/p>\n","protected":false},"excerpt":{"rendered":" Review of the book “Reckoning with Risk” and its applicability to the case of Andrew Stimpson<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","footnotes":""},"categories":[23,24,29,47],"tags":[],"class_list":["post-128","post","type-post","status-publish","format-standard","hentry","category-based-on-a-true-story","category-cathartic-rant","category-influencing-others","category-review"],"_links":{"self":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts\/128","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/comments?post=128"}],"version-history":[{"count":0,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts\/128\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/media?parent=128"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/categories?post=128"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/tags?post=128"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}