2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/202478We discuss fitting correlated data - with the example of hadron mass spectroscopy in mind. The main conclusion is that the method of minimising correlated $χ^2$ is unreliable if the data sample is too small.10 pages, LATEX, 1 postscript figure enclosed, Liverpool LTH 321High Energy Physics - Latticetext