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Category: Blog

Linear models for quantiles

Most statistical models used in experimental psychology are designed to estimate the mean of a response variable given some set of predictors. This is all well and good when errors are largely symmetric and our predictors are expected to primarily … Read more

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Factorizing motion trajectories

It’s difficult to analyze trajectory data, since the “object” of analysis (the trajectory) can’t easily be summarized by a single value without throwing away large amounts of information, unless you already know what you’re looking for (e.g. if you’re looking … Read more

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Publication quality plots in R

The trend is slowly moving towards interactive plotting and reproducible research with e.g. knitR (which I fully support), but it seems to me that R/ggplot2 is still the best plotting system for static graphics. That said, ggplot’s stock settings … Read more

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Mixture modelling for reaction time distributions

I’m swimming in reaction time data at the moment. My usual approach to analyzing reaction times in cognitive psychology is through some sort of normal random effects model of the log or inverse RT. This is really only good for … Read more

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A note on the CLT

Introductory statistics courses (particularly when they’re taught outside of the statistics department) often gloss over the details of the central limit theorem, describing it only as something that let’s you do t-tests without worrying about normality. I recently came across … Read more

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Echo-state networks in R

Echo-state networks (ESN’s) are a class of neural network designed to work with temporal data. I normally don’t like neural networks, since they rarely actually tell you anything interpretable about your data (and they pretty much just do regression anyway), … Read more

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Robust t-regression

I’ve been experimenting with techniques for robust regression, and I thought that it would be a fun excercise to implement a robust variant of the simple linear regression model based on the t-distribution.


The term “outlier” is used very … Read more

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Doing meta-analysis II

I recently collaborated on a meta-analysis investigating the effects of blast-related (i.e. *BOOM*) mild traumatic brain injury (mTBI) on cognitive performance (Karr, et al. 2014). Each of the eight included studies used control and mTBI groups, and reported means and … Read more

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Doing meta-analysis I

Meta-analysis is, broadly, a set of statistical models for combining the results of several research studies in order to summarize the literature, or estimate an effect more precisely than can be done by a single study alone. The actual process … Read more

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