Statistical illiteracy afflicts health care professionals and their patients

Over at Scientific American Mind Gerd Gigerenzer and his colleagues have published a terrific article documenting the statistical illiteracy that sometimes runs rampant in health care fields. The article, "Knowing Your Chances," appears in the April/May/June 2009 edition. The authors point out numerous medical care fallacies caused by statistical illiteracy , including Rudy Giuliani's 2007claim that because 82% of Americans survived prostate cancer, compared to only 44% in England, that he was lucky to be living in the United States and not in England. This sort of claim is based on Giuliani's failure to understand statistics. Yes, in the United States, men will be more quickly diagnosed as having prostate cancer (because many more of them are given PSA tests), and then many more of them will be treated. Despite the stark differences in survival rates (the percentage of patients who survive the cancer for a least five years, "mortality rates in the two countries are close to the same: about 26 prostate cancer deaths per 100,000 American men versus 27 per 100,000 in Britain. That fact suggests the PSA test

has needlessly flagged prostate cancer in many American men, resulting in a lot of unnecessary surgery and radiation treatment, which often leads to impotence or incontinence. Because of overdiagnosis and lead-time bias, changes in five-year survival rates have no reliable relation to changes in mortality when patterns of diagnoses differ. And yet many official agencies continue to talk about five-year survival rates.

Gigerenzer and his colleagues give a highly disturbing as example regarding mammogram results. Assume that a woman just received a positive test result (suggesting breast cancer) and asks her doctor "What are the chances that I have breast cancer?" In a dramatic study researchers asked 160 gynecologists taking a continuing education course to give their best estimate based upon the following facts:

A.) the probability that a woman has breast cancer (prevalence) is 1% B.) if a woman has breast cancer the probability that she tests positive (sensitivity) is 90% C) if a woman does not have breast cancer, the probability that she nonetheless tests positive (false-positive rate) is 9% The best answer can be quickly derived from the above three statements. Only about one out of 10 women who test positive actually has breast cancer. The other 9/10 have been falsely diagnosed. Only 21% of physicians picked the right answer. 60% of the gynecologists believed that there was either an 81% or 90% chance that a woman with a positive test result actually had cancer, suggesting that they routinely cause horrific and needless fear in their patients. What I found amazing is that you can quickly and easily determine that 10% is a correct answer based upon the above three statements--simply assume that there are 100 patients, that one of them (1%) actually has breast cancer and that nine of them (9%) test false positive. This is grade school mathematics: only about 10% of the women testing positive actually have breast cancer. As the article describes, false diagnosis and bad interpretations often combine (e.g., in the case of HIV tests) to result in suicides, needless treatment and immense disruption in the lives of the patients. The authors also discuss the (tiny) increased risk of blood clots caused by taking third-generation oral contraceptives. Because the news media and consumers so often exhibit innumeracy, this news about the risk was communicated in a way that caused great anxiety. People learned that the third-generation pill increased the risk of blood clots by "100%." The media should have pack is aged the risk in a more meaningful way: whereas one out of 7000 women who took the second-generation pill had a blood clot, this increased to two in 7000 women who took the new bill. The "absolute risk increase" should have been more clearly communicated. Check out the full article for additional reasons to be concerned about statistical illiteracy.

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Who I Am Is No One Else’s Business

As this just happened, I thought I'd come right home and write about it. I just had one of those customer service incidents that sends me over the moon. I walked into a store to find something. I was in a frame of mind to buy. I found the something and asked the sales person "How much is that?" Back at her desk, she sat down, I sat down, and I expected her to punch up the price on her computer and tell me. Instead: "What's you name?" "Private individual," I replied, a bit nonplussed. "I need a name for the quote," she said. "You have to have it?" "Yes." "Have a nice day." And I walked out. Now, this was perhaps petty of me. What, after all, is the big deal? She needed to punch a name into her computer to open the dialogue box to ask for the price. Here's the big deal: IT'S NONE OF YOUR DAMN BUSINESS WHO I AM UNTIL I DECIDE TO BUY FROM YOU! This is a persistent and infuriating condition in our present society that causes me no end of irritation because so few people think it is a problem that I end up looking like a weirdo because I choose not to hand out private information for free. It has crept up on us. Decades ago, when chain stores began compiling mailing lists by which they could send updates and sale notices to their client base. Then they discovered they could sell those lists to other concerns for marketing. Now we have a plague of telemarketers, junk mail, spam, and cold calls and a new social category with which to look askance at people who would prefer not to play. Like me. In itself, it is an innocent enough thing. But it is offensive, and what offends me the most is my fellow citizens failing to see how it is offensive and how it on a deep level adds to our current crisis. Look: if telemarketing didn't work, no one would do it. A certain percentage of those unwanted calls actually hook somebody into buying something. Direct mail campaigns have an expected positive return rate of two percent. That is considered normal response and constitutes grounds to continue the practice. Economies of scale work that way. So if only two to five percent of the public respond favorably to the intrusions of these uninvited pests, they have reason to persist. I think it might be fair to say that people with money and education don't respond as readily as poorer, less educated folks who are always on the lookout for bargains---and often find bargains they don't understand and probably end up costing them too much, like sub prime mortgages. We are too free with our personal information. Maybe you or you or you find nothing wrong with always giving out your phone number or your zip code or even your name and address when asked, in Pavlovian response to the ringing bell behind the counter, but what has happened is that we have made available a vast pool of data that makes it easy to be imposed upon and that has aided and abetted a consumer culture that has gotten out of hand. And made those of us who choose not to participate in this look like some form of misanthropic libertarian goofballs. How hard is this? If I choose to buy from someone, then I have agreed to have a relationship, however tenuous, with them. Unless I pay cash, they are entitled to know with whom they are dealing. But if I'm not buying, they have no right to know who I am. And I can't know if I'm going to buy if I don't know how much the object in question is. Trying to establish the buying relationship in advance of MY decision to buy is...rude. I have walked out of many stores when confronted with a request for personal information. I've had a few shouting matches with managers over it. In some instances, the unfortunate salesperson is as much a victim, because some software programs these days have as a necessary prerequisite for accessing the system the entry of all this data. The corporation won't even let the employee make the call whether it's worth irritating someone over collecting all this information. Concerns and worries over Big Brother have a certain validity, but it is largely unremarked that the foundation of such a system will not be imposed on us---rather we will hand the powers that be what they ask for because we can't muster up enough sense of ourselves to say, consistently, "None of your damn business!" There. I feel better. I needed to get that out. This rant has been brought to you by Consumer Culture LTD.

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Frank Schaeffer lays, and takes, the blame for murder –

I found this an interesting response to George Tiller's murder. Frank Schaeffer, a reformed evangelical, argues that the hate speech continually spewed by the religious right regarding abortion set the stage for George Tiller's murder, and other abortionists before him. He still expresses disgust at late-term abortion, and while I am more likely to agree with that, I do believe there are situations in which that choice is the only one that makes sense. Painful, horribly so, but sometimes the only choice is.

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Darfur, lest we forget –

Bob Herbert, in the NY Times, wrote this week of a new report on the continuing human catastrophe in Darfur. In describing why he reported on what, to some, is old news, he reminded us "about the dangers inherent in indifference to the suffering of others. Stories of atrocities on the scale of those coming out of Darfur cannot be told too often."

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Oklahoma trooper clashes with paramedic

This has got to be one of the most idiotic things I've ever seen, on many levels: an Oklahoma trooper pulling over an ambulance for a traffic violation and threatening to arrest one of the paramedics. And, oh yeah . . . the ambulance was trying to convey a woman to the hospital at the time.

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