Monday, September 30, 2013

The Remarkable Milton Friedman

Some start for a positivist. In 1977, Hayek reminded us that Milton Friedman was "an arch-positivist who believes nothing must enter scientific argument except what is empirically proven."  Yet, Friedman couldn't even get physical empirical correlations correct, when only around a half dozen variables were involved.

During an interview conducted by John Taylor he said:
There was a big project during the war of trying to determine the alloy that would have the greatest strength under high temperatures. We were called in as statistical consultants to the various groups working on the problem. I had a lot of data from all their experiments. I computed a multiple regression using these data--data that had been derived from hanging a weight on an experimental turbine blade to see how long it took for the blade to rupture at a given temperature. I regressed the length of time to rupture on the chemical composition and various other variables based on metallurgical theory I could find. I got an excellent correlation. So I used my regression to predict what new alloys would have a longer time before rupture, I got wonderful results even though I insisted on restricting  every variable separately to the range of values that had been used in the experiment. My equation predicted something like 200 hours until rupture for my constructed alloy, That would have been an enormous success compared to existing alloys.

Unlike in economics, we could put the prediction to a test. I called some people up at MIT and they constructed this alloy and tested it. It was an utter failure! That taught me that you could not depend on a narrow range of evidence using a lot of variables. I think I had a half-dozen or more variables.

4 comments:

  1. The link to the book on Amazon says that Hayek was "not correct" in claiming that Friedman was "an arch-positivist who believes nothing must enter scientific argument except what is empirically proven."

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    1. Jerry Wolfgang = George selgin

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  2. Please see _Engine Revolutions:The Autobiography of Max Bentele_, SAE, 1991, ISBN 1-56091-081-X.

    Bentele was involved in developing almost every engine type, from turbines to rotary engines, in the 20th century. In the development of the turbine, he was in-your-face sure of his work and his calculations. The fracturing of turbine blades came about because of a 7th harmonic resonance and it was Bentele who forced the industry - German and Others - to examine the first principles in order to get it right.

    Friedman could have studied alloys for the rest of his life and never made progress. In a similar manner, Einstein didn't know about the Strong Force and could never have achieved his dream of Unification with the tools he had.

    Mere mathematical technique is simply not enough.

    CW

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