Q&A with Stephen Ziliak co-author of The Cult of Statistical Significance

by University of Michigan Press on September 10, 2008

The Cult of Statistical SignificanceStephen Ziliak and Deirdre McCloskey have published a new book: The Cult of Statistical Significance: How the Standard Error Costs Us Jobs, Justice, and Lives (University of Michigan Press, 2008).

Question: How, if at all, can a book on statistics deal with issues of social justice?

Stephen Ziliak (“Prof Z”): Good question! For years, I, like most people, did not see any connection at all between statistics and social justice, or, to say it more generally, between statistics and ethics. It wasn’t until 1989 – while working at the Indiana Department of Workforce Development – that I saw for the first time how deeply human the seemingly arcane and “objective” world of statistics is.

I worked in the Labor Market Information Division, where the official state and regional labor force statistics are generated and disseminated in cooperation with the U.S. Department of Labor. One day a citizen telephoned. He asked me to provide unemployment rate statistics for black youth in each of Indiana’s major cities. Young men and women between the ages of 16 and 21. I couldn’t find the statistics he asked for. Now Indianapolis, Gary, Fort Wayne, Evansville had then as now tragically high amounts of minority unemployment – and very high for young African American men in particular. No one would be surprised if the average city rate exceeded 35 or 40% while the national rate – for the whole economy – was only around 5%. So where were the statistics proving it?

Finally I went to the chief of my division. He made a phone call to the Chicago branch of the U.S. Department of Labor, to a chief who was next in line in the chain of command. The chief in Chicago replied “given the lack of statistical significance in the black youth unemployment rates, the Department of Labor does not disseminate those rates. We don’t publish statistically insignificant results, only “significant” results,” he said. I was embarrassed to return to the telephone to tell the citizen what I learned.

What the Labor Department was saying is that if a rate is not estimated with an arbitrary amount of precision then they won’t publish or disseminate it. In technical terms, the p-value has to be equal or less than .10. This standard they glue to even if other evidence suggests that the rate is so high as to constitute what Martin Luther King Jr. called a “Great Depression in the economy of the ghetto.” It was a life-changing experience for me. I realized that important social issues get pushed under the rug for pseudo-scientific reasons. But as I show in The Cult very few scientists have had this kind of realization. That precision is not the end all be all of human decision making. Like most members of the cult of statistical significance, the DOL economists and statisticians – my friends and former bosses – do not possess or implement a scientifically legitimate or socially just decision rule. Zero, nil, null, nothing. It has to change.

Question: What was your favorite part about working on the book?

Prof Z: I love to do what historians call “archival research” – the scientific and humanistic study of old manuscripts and data. I started my career as an economic historian and historian of ideas. Historical wisdom is I think one of the best forms of wisdom which one can acquire in a field such as economics. If you want to know whether abolishing welfare is a good idea, the first thing to do is to see what happened in the past – before and after previous attempts as welfare abolition. If you want to know if wage and price controls work then go to periods in history when they’ve been implemented and you can study those effects. Well, anyway, to answer your question, the relevant archives for this book are located at University College London, the Guinness Brewery in Reading, Dublin, Ireland, and at the University of Reading, UK. So yeah, besides the joy I get blowing the dust off original manuscripts – in the event, the works of great scientists such as William Sealy Gosset (asa “Student”), Karl Pearson, Egon Pearson, Ronald Fisher, and Jerzy Neyman – I certainly enjoyed my stays in Ireland and the UK.

Question: You’ve been an economics professor at Roosevelt since 2003. What did you do before that?

Prof Z: For four years I taught at Emory University and for three of them (overlapping) I also taught at the Georgia Institute of Technology. Previously I was an assistant professor of economics at Bowling Green State University. And before that I was working on my Ph.D. in Economics and my Ph.D. Certificate in the Rhetoric of Human Inquiry, both at the University of Iowa. The phone call about black unemployment rates came about a year before I left my government job for graduate study in Iowa. I’ve held a lot of non-academic jobs – for example, I used to be a welfare caseworker, doing home visits, the whole nine yards.

Question: Did you use information resources or libraries while working on the book?

Prof Z: Yes, I sure did, and still do. The inter-library loan system, the UIC libraries, and the University of Chicago libraries were on top of Roosevelt’s Murray-Green a fantastic help. The only problem I face is that I need the books for longer periods of time than the system currently accommodates. Perhaps we can make a change on that front. Real scholarship takes years to produce – especially in technical fields such as economics and statistics.

Question: What is one thing that you would like people to experience from reading the book?

Prof Z: I would like people to feel in their bones the following maxim: “Precision is nice but Oomph is the bomb.” But to feel it – to understand it – you’ll have to read the book! Knowing the difference between precision and oomph can save lives, jobs, justice and the environment.

Interview above with “Prof Z” (Stephen Ziliak) originally published as an interview with David Pribyl, Head of Technical Services at the Roosevelt University Library.

For more about The Cult of Statistical Significance: How the Standard Error Costs us Jobs, Justice, and Lives by Stephen T. Ziliak and Deirdre N. McCloskey, visit: www.press.umich.edu/titleDetailDesc.do?id=186351

Comments on this entry are closed.

Previous post:

Next post: