The proposal of Collie et al for determining reliable change in sports medicine and their review of other current procedures did not address mathematical or theoretical aspects. This article attempts to fill this lacuna, in order to examine the validity of their proposal and the suitability of their review. The conclusions drawn are that Collie et al presented their method too carelessly and their review of other methods leaves serious drawbacks and mistakes unnoticed. A scheme is here provided showing which of the current methods can be used in which situation.