Blog Archives

How Do You Write Your Model Definitions?

October 20, 2013
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How Do You Write Your Model Definitions?

I’m often irritated by that when a statistical method is explained, such as linear regression, it is often characterized by how it can be calculated rather than by what model is assumed and fitted. A typical example of this is that linear regression is often described as a method that uses ordinary least squares to calculate the best...

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A Bayesian Twist on Tukey’s Flogs

September 30, 2013
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A Bayesian Twist on Tukey’s Flogs

In the last post I described flogs, a useful transform on proportions data introduced by John Tukey in his Exploratory Data Analysis. Flogging a proportion (such as, two out of three computers were Macs) consisted of two steps: first we “started” the proportion by adding 1/6 to each of the counts and then we “folded” it...

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Going to Plot Some Proportions? Why not Flog ‘em First?

September 23, 2013
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Going to Plot Some Proportions? Why not Flog ‘em First?

Fractions and proportions can be difficult to plot nicely for a number of reasons: If the proportions are based on small counts (e.g., two of his three computing devices were Apple products) then the calculated proportions will only take on a number of discrete values. Depending on what you have measured there might be many proportions close to the...

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SPSS looked great! 20 years ago…

September 4, 2013
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SPSS looked great! 20 years ago…

For some reason someone dropped a pamphlet advertising SPSS for Windows 3.0 in my mail box at work. This means that the pamphlet, and the advertised version of SPSS, should be at least 20 years old! These days I’m happily using R for everything but if I was going to estimate any models 20 years ago SPSS actually looked...

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Bayesian Estimation of Correlation – Now Robust!

August 28, 2013
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Bayesian Estimation of Correlation – Now Robust!

So in the last post I showed how to run the Bayesian counterpart of Pearson’s correlation test by estimating the parameters of a bivariate normal distribution. A problem with assuming normality is that the normal distribution isn’t robust against outliers. Let’s see what happens if we take the data from the last post with the finishing times...

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The Bayesian Counterpart of Pearson’s Correlation Test

August 19, 2013
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The Bayesian Counterpart of Pearson’s Correlation Test

Except for maybe the t test, a contender for the title “most used and abused statistical test” is Pearson’s correlation test. Whenever someone wants to check if two variables relate somehow it is a safe bet (at least in psychology) that the first thing to be tested is the strength of a Pearson’s correlation. Only if that doesn’t...

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Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model: Part three.

August 11, 2013
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Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model: Part three.

In part one and part two of Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model I developed a model for the number of goals in football matches from five seasons of La Liga, the premier Spanish football league. I’m now reasonably happy with the model and want to use it to rank...

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Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model: Part two.

July 28, 2013
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Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model: Part two.

In the last blog post I showed my initial attempt at modeling football results in La Liga using a Bayesian Poission model, but there was one glaring problem with the model; it did not consider the advantage of being the home team. In this post I will show how to fix this! I will also show a way...

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Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model: Part one.

July 21, 2013
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Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model: Part one.

This is a slightly modified version of my submission to the UseR 2013 Data Analysis Contest which I had the fortune of winning :) The purpose of the contest was to do something interesting with a dataset consisting of the match results from the last five seasons of La Liga, the premium Spanish football (aka soccer) league. In...

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useR 2013 was a blast!

July 14, 2013
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useR 2013 was a blast!

I had a great time at useR 2013 in Albacete, Spain. The food was great, the people were fun and the weather was hot. A pleasant surprise was that I won the useR data analysis contest with my submission “Modeling Match Results in La Liga Using a Hierarchical Bayesian Poisson Model.” It was a fun exercise modeling football...

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