Beer sampling

A recent column from Tim Harford explains how an early Guinness brewer contributed to our understanding of statistics:

The statistical apparatus to check this is a test called Student’s t-test. Student was the pseudonym of William Sealy Gosset, an amiable, rucksack-wearing chemist who – beginning in 1899 – worked all his adult life for Guinness and eventually rose to the rank of head brewer. So nervous was the company about commercial confidentiality that Gosset published surreptitiously under his pseudonym.

From the outset, Gosset’s focus was practical – as the economist and historian Steve Ziliak has discovered through his work in the Guinness archives. To produce beer to a high standard on an industrial scale, Gosset needed to sample and experiment with hops, malt and barley. But experiments are expensive and Gosset developed his small-sample methods because he wanted to understand how many experiments were necessary to be confident of his results. That was a clear trade-off: how much confidence is “enough” depends on the costs of further research and the benefits of extra precision.

The article is interesting throughout. Give it a read and have something to tell your friends about when you have a very large sample of Guinness pints for St. Patrick’s Day later this month.

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Lazy reporting and the Pueblo ban study

The Centers for Disease Control have issued a new report about the impact of the smoking ban in Pueblo, Colorado. The study has the media breathlessly repeating claims that the ban dramatically saves lives. “A smoking ban caused heart attacks to drop by more than 40 percent in one U.S. city and the decrease lasted three years, federal health experts reported Wednesday,” writes Reuters reporter Maggie Fox, who doesn’t bother quoting any dissenting sources. Mary Engle at the LA Times health blog says uncritically that whatever the mechanism behind the fall in heart attacks, “Pueblo’s smoking ban can take the credit.” Bill Scanlon at the Rocky Mountain News throws science to the wind and extrapolates that Colorado will see a statewide “sharp decline” in heart attacks in 2009 — more than two years after its ban went into effect.

I realize times are tough in newsrooms, but there’s no excuse for such biased, lazy reporting. Journalists should treat the claims of ideologically driven anti-smoking groups with just as much skepticism as they would junk science coming from big tobacco companies.

Since the CDC’s report is going to be cited constantly by smoking ban advocates it’s worth taking a look at its methodology and limitations. Fortunately it’s straightforward enough that any moderately intelligent person can understand it. The following is my layman’s reading of the results, with the caveat that I’m approaching this without formal training. Nonetheless, it’s clear that one shouldn’t take this study’s conclusions at face value. Its use by anti-smoking groups, researchers, and the press to promote smoking bans is a case study in the abuse of science for political ends.
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