Statistics for the non-statistician. I: Different types of data need different testsBMJ 1997; 315 doi: https://doi.org/10.1136/bmj.315.7109.675 (Published 13 September 1997) Cite this as: BMJ 1997;315:675
An author's error appeared in this article by Trisha Greenhalgh (9 August, pp 364-6). In table 1, the χ2 test is listed as a parametric test. In fact, both the χ2 test and Fisher's exact test are non-parametric.