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Sunday, April 08, 2007

Expert’s judgments skewed by biases?

Subject matter expertise from a technical guru often works wonders. For example, consider Charles Steinmetz of General Electric, who learned his trade from Thomas Edison. Steinmetz invented more than 200 electrical devices. It’s said that after he retired, GE hired Steinmetz to solve a particularly difficult machine problem. He looked here and there, tested various parts, and then marked an "X" on a specific spot. The GE engineers were amazed to find a defect precisely at the Steinmetz mark. Later they got a bill for $1,000. The itemization read: "For making one chalk mark - $1. For knowing where to put it - $999."

Many years ago (40!*) as a pre-teen I read the story “Eleven Blue Men” by Berton Roueché. This and other true stories about medical detectives fascinated me. Given the popularity of the television show House, I am not the only one who appreciates experts that make astoundingly accurate diagnoses based on a few facts and fantastic leaps of intuition.

Dr. Jerome Groopman in his book on How Doctors Think says that “The mind acts like a magnet, pulling in clues from all directions.” However, Groopman advises experts keep their guard up against these common biases:
- Availability – the tendency to reach for the easiest plausible explanation and reject all others,
- Confirmation – see only evidence that fits preconceived notions,
- Commission – the rush to action when doing nothing would be best.
(If you never want to believe any expert opinion again, see an exhaustive list of cognitive errors in diagnosis compiled by Dr. Pat Croskerry (Dalhousie University Faculty of Medicine, Halifax, Nova Scotia, Canada).)

Groopman suggests that patients who fear they are not getting a good diagnosis ask these simple questions: “What else could it be? Could two things be going on simultaneously?” This strikes a chord with me as a specialist in the field of experiment design. It seems that the toughest problems for those who rely on intuition, or heuristics as Groopman calls it, are those where factors interact to create an important effect.

By the way, Groopman has some interesting caveats about the new approach of “evidence-based medicine,” which you can see in an excerpt from his book posted along with the sound track of an interview by NPR’s “Morning Edition” radio show. He warns, “Statistics embody averages, not individuals.

*PS. Yes, I do feel old, but age may provide some benefit via the accumulation of experience. For example, the March 22nd issue of Wall Street Journal says that age 53 is best for financial decisions. “The age of reason” they call it. Guess how old I am. It’s funny how one notices stuff like this that confirms a prior notion.


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