Posts Tagged ‘ Uncategorized ’

Thinking of doing a list experiment? Here’s a list of reasons why you should think again

April 23, 2014
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Someone wrote in: We are about to conduct a voting list experiment. We came across your comment recommending that each item be removed from the list. Would greatly appreciate it if you take a few minutes to spell out your recommendation in a little more detail. In particular: (a) Why are you “uneasy” about list […]The post Thinking of doing a list experiment? Here’s a list of reasons why you…

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The inverse of the Hilbert matrix

April 23, 2014
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The inverse of the Hilbert matrix

Just one last short article about properties of the Hilbert matrix. I've already blogged about how to construct a Hilbert matrix in the SAS/IML language and how to compute a formula for the determinant. One reason that the Hilbert matrix is a famous (some would say infamous!) example in numerical […]

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Picking a (bio)statistics thesis topic for real world impact and transferable skills

April 22, 2014
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One of the things that was hardest for me in graduate school was starting to think about my own research projects and not just the ideas my advisor fed me. I remember that it was stressful because I didn't quite … Continue reading →

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Seven forecasting blogs

April 22, 2014
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Seven forecasting blogs

There are several other blogs on forecasting that readers might be interested in. Here are seven worth following: No Hesitations by Francis Diebold (Professor of Economics, University of Pennsylvania). Diebold needs no introduction to forecasters. He primarily covers forecasting in economics and finance, but also xkcd cartoons, graphics, research issues, etc. Econometrics Beat by Dave Giles. Dave is a professor of economics at the University of Victoria (Canada), formerly from my own…

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Local functions (not!) in the SAS/IML language

April 21, 2014
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Local functions (not!) in the SAS/IML language

I have previously written about the scope of local and global variables in the SAS/IML language. You might wonder whether SAS/IML modules can also have local scope. The answer is no. All SAS/IML modules are known globally and can be called by any other modules. Some object-oriented programming languages support […]

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Correlation does not imply causation (parental involvement edition)

April 17, 2014
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The New York Times recently published an article on education titled "Parental Involvement Is Overrated". Most research in this area supports the opposite view, but the authors claim that "evidence from our research suggests otherwise".  Before you stop helping your children … Continue reading →

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Errors on percentage errors

April 16, 2014
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Errors on percentage errors

The MAPE (mean absolute percentage error) is a popular measure for forecast accuracy and is defined as     where denotes an observation and denotes its forecast, and the mean is taken over . Armstrong (1985, p.348) was the first (to my knowledge) to point out the asymmetry of the MAPE saying that “it has a bias favoring estimates that are below the actual values”. A few years later, Armstrong…

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On the determinant of the Hilbert matrix

April 16, 2014
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On the determinant of the Hilbert matrix

Last week I described the Hilbert matrix of size n, which is a famous square matrix in numerical linear algebra. It is famous partially because its inverse and its determinant have explicit formulas (that is, we know them exactly), but mainly because the matrix is ill-conditioned for moderate values of […]

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Generating tables in LaTeX

April 14, 2014
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Generating tables in LaTeX

Typing tables in LaTeX can get messy, but there are some good tools to simplify the process. One I discovered this week is tablesgenerator.com, a web-based tool for generating LaTeX tables. It also allows the table to saved in other formats including HTML and Markdown. The interface is simple, but it does most things. For complicated tables, some additional formatting may be necessary.     Similar functionality is available via…

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Summary of new features in SAS/IML 12.1

April 14, 2014
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Summary of new features in SAS/IML 12.1

I enjoy blogging about new functionality in the SAS/IML language because I can go into more depth and provide more complicated examples than the SAS/IML documentation. Today's article is a summary of all of my posts about features that were added to SAS/IML 12.1, which shipped in August 2012 as […]

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