Psychological Statistics: 2013

Multicollinearity and collinearity (in multiple regression) - a tutorial

This blog post was written for undergraduate research methods teaching. I have therefore tried to keep everything relatively simple and equation-free. The content is based loosely on more detailed material in my book Serious stats.

What are collinearity and multicollinearity?

Collinearity occurs when two predictor variables (e.g., x1 and x2) in a multiple regression have a non-zero correlation. Multicollinearity occurs when more than two predictor variables (e.g., x1, x2 and x3) are inter-correlated.

How common is collinearity or multicollinearity?

If you collect observational data or data from a non-experimental or quasi-experimental study collinearity or multicollinearity will nearly always be present.

Aug

Cronbach to the future

One fascinating thing about working in the area of psychological statistics is how hard it is to move people away from reliance on bad, inefficient or otherwise problematic methods. My own view - informed to some extent by the literature, by experience and by anecdote is that it isn't sufficient merely to establish than the standard approach is wrong. It isn't even sufficient to provide an obviously superior alternative.

Jun

Why faking data is bad ...

It never occurred to me until today to write a post about why faking data is bad. However, I noticed an interesting exchange on Andrew Gelman's blog (see the comments on this post about Marc Hauser).

Jun

Serious stats: using multilevel models to get accurate inferences for repeated measures ANOVA

This article from my other blog may be of interest to readers of this blog: http://seriousstats.wordpress.com/2013/04/18/using-multilevel-models-to-get-accurate-inferences-for-repeated-measures-anova-designs/

Apr

Neuroscience, statistical power and how to increase it

There has been quite a bit of buzz recently about the Button et al. Nature Reviews Neuroscience paper on statistical power. Several similar reviews have been published in psychology and other disciplines and come to broadly the same conclusion - that most studies are underpowered. The main difference with the Button et al.

Apr

Reflecting on the end of history illusion illusion

A while back Jon Sutton at The Psychologist asked my opinion on the end of history illusion. This was sparked by an interesting Science paper by Quoidbach, Gilbert and Wilson. Blogger and mathematician Jordan Ellenberg had written a blog post arguing that the paper makes a mistake: "a somewhat subtle mistake, but a bad mistake, and one which kills a big chunk of the paper".

Jon wanted a second opinion, and after a bit of reading I replied that Ellenberg's criticisms were valid.

Jan

The growth of Bayesian methods in psychology

The British Journal of Mathematical and Statistical Psychology has published a target article (with commentaries and reply) by Andrew Gelman and Cosma Shalizi on philosophy and the practice of Bayesian statistics.

Mark Andrews and I introduce the target article with an editorial aimed at providing some background to psychologists who are interested in Bayesian statistics but need a little back story.