Research Article How to do it. Choose and use a calculator. Br Med J 1979; 1 doi: http://dx.doi.org/10.1136/bmj.1.6159.326 (Published 03 February 1979) Cite this as: Br Med J 1979;1:326 Article Related content Metrics Responses Peer review This article has a correction. Please see:Correction: How to do it: Choose and use a calculator - February 17, 1979 This is a PDF-only article. The first page of the PDF of this article appears below.