In general, a correlation test is used to test the association between two variables (y and z). However, if there is a third variable (x) that might be related to z or y, it makes...

In general, a correlation test is used to test the association between two variables (y and z). However, if there is a third variable (x) that might be related to z or y, it makes...

Inspired by this blog post from theBioBucket, I created a script to parse all pdf files in a directory. Due to its reliance on the Terminal, it’s Mac specific, but modifications for other systems shouldn’t be too hard (as a start for Windows, see BioBucket’s script). First, you have to install the command line tool

The next minor update to R — version 2.15.2 "Trick or Treat" — will be released on October 26, R-core member Peter Dalgaard announced today. You can find the planned updates in the current NEWS file (scroll down to the section 'CHANGES IN R VERSION 2.15.1 patched'; the changes at the top of the file are planned for the...

Power analysis is a very useful tool to estimate the statistical power from a study. It effectively allows a researcher to determine the needed sample size in order to obtained the required statistical power. Clients often ask (and rightfully so) what the sample size should be for a proposed project. Sample sizes end up being

Around two years ago, I suddenly realized my statistical training had a great big Bayes-shaped hole in it. My formal education in statistics was pretty narrow – I got my degree in anthropology, a discipline not exactly known for its rigorously systematic analytic methods. I learned the basics of linear models and principal components analysis

Suppose that you accepted my argument from the last two posts on halo effects and bifactor models. As you might recall, I argued that when respondents complete rating scales, they predominating rely on their generalized impression with a more minor role played by the specific features that the ratings were written to measure. Consequently, we...

This course is running 1-5 October at the University of Essex. There doesn’t seem to be a website but you register by writing to [email protected] Here’s what they say in their e-mail: Lecturers: Dr Werner Adler (University of Erlangen-Nuremberg; Co-author … Continue reading →