Monday, July 9, 2012

The God particle and stats...

We all know by now that CERN announced the discovery of the long-sought Higgs particle (or the so called God particle) last Wednesday. This is a discovery about nothing – that is it describes what is occurring in the vacuum. This achievement is huge considering it culminates literally decades of effort by thousands of physicists and engineers spending billions of euros to build the Large Hadron Collider. But the media’s reporting of 5-sigma as a measure of “certainty” was also remarkable.

First the vacuum - A vacuum is a space entirely devoid of matter and so represents a least possible energy state. Peter Higgs, and others realized that the state with least energy needn’t be empty - it can instead be filled with a physical quantity that slows down [electron] and gives mass to everything we know.

As mentioned some media outlets associated 5-sigma as a measure of certainty for the discovery of the Higgs boson. The gold standard for a discovery is a "5-sigma" bump, where sigma is a measure of bumpiness or standard deviation. A bump that high means that the odds are less than 1 in 3.5 million that it was produced by chance.

For instance, the science editor at the Swedish news paper Dagens Nyheter reported that a sigma of 4.9 equals a certainty of 99.99994%, which obviously isn’t true, simply because p(D|H0 ) is not the same as p(H0|D) meaning p-value represents the conditional probability of getting the data given that the null hypothesis is true. Nothing more, and it surely doesn’t give the probability for the alternative hypothesis being true, Ala the “certainty” that something has been found that’s not a random fluctuation.

1 comment:

  1. The term "God Particle" came from the book "The God Particle / If the Universe is the Answer, What is the Question?," by Leon Lederman & Dick Teresi (Houghton Mifflin Harcourt, Jun 26, 2006), which is in the bibliography of my free ebook on comparative mysticism.

    In the Preface to his book Dr. Lederman, a Nobel laureate in physics, wrote:
    Now as for the title, The God Particle, my coauthor, Dick Teresi, has agreed to accept the blame. I mentioned the phrase as a joke once in a speech, and he remembered it and used it as the working title of the book. "Don't worry," he said, "no publisher ever uses the working title on the final book." The title ended up offending two groups: 1) those who believe in God and 2) those who do not. We were warmly received by those in the middle.