Articles by Thom

CIs for Spearman’s rho and Kendall’s tau

May 18, 2020 | Thom

There are various methods for obtaining CIs for Kendall’s tau and Spearman’s rho. As the underlying data are unlikely to be bivariate normal (or else Pearson’s r would be used) bootstrapping is often recommended – but it doesn’t always perform that well (Bishara & Hittner, 2017). One could also ... [Read more...]

Chi-Square and the Egon Pearson correction

September 5, 2019 | Thom

Looking back at the coverage of the Chi-Square test of independence in the book there are a couple of things I wish I’d gone into greater depth on. First, resolving the debate on the appropriate way to handle small expected values in the test of independence. Second, expanding on ... [Read more...]

VIF and multicollinearity diagnostics

May 31, 2017 | Thom

In the book I use the car package to get VIF and other multicollinearity diagnostics. I’ve occasionally found this breaks down (usually through mixing different versions of R on different machines at work home or on the move). I recently saw the mctest package and thought it would be ... [Read more...]

Near-instant high quality graphs in R

September 5, 2012 | Thom

One of the main attractions of R (for me) is the ability to produce high quality graphics that look just the way you want them to. The basic plot functions are generally excellent for exploratory work and for getting to know your data. Most packages have additional functions for appropriate ... [Read more...]

Pasting Excel data into R on a Mac

June 2, 2012 | Thom

When starting out with R, getting data in and out can be a bit of a pain. It should take long to work out a convenient method – depending on what OS you use and what other packages you work with. In my case I prefer to work with Excel spreadsheets (... [Read more...]

R functions for serious stats

March 25, 2012 | Thom

UPDATE: Some problems arose with my previous host so I have now updated the links here and elsewhere on the blog. The companion web site for Serious Stats has a zip file with R scripts for each chapter. This contains examples of R code and and all my functions from ... [Read more...]

Beware the Friedman test!

February 14, 2012 | Thom

In section 10.4.4 of Serious stats (Baguley, 2012) I discuss the rank transformation and suggest that it often makes sense to rank transform data prior to application of conventional ‘parametric’ least squares procedures such as t tests or one-way ANOVA. There are several advantages to this approach over the usual approach (which ... [Read more...]

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