How many participants do I need? A worked sample size example
A sample size calculation for comparing two group means, with the power curve behind it, in base R.
Sep 7, 2026
Alexander van Twisk
Biostatistician. PhD student at the MRC Biostatistics Unit, University of Cambridge.
I work on how clinical trials can adapt as they learn, and on making good statistics practical for the researchers who need it. I write here about statistics, R, and trial methodology, and now and then about aviation and history.
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CV
Degrees, roles, talks, and research projects.
About
The path from applied mathematics to trial methodology, and what the PhD is about.
Consulting
Statistical support for researchers in the medical and public health sciences, from study design to publication.