In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old. Such investigations are often analysed inappropriately, notably by using correlation coefficients. The use of correlation is misleading.

Bland and Altman developed their analysis to address the inappropriate use of the correlation coefficient as a means of comparing 2 methods of measuring the same clinical parameter. However, a careful reading of their manuscript shows that the short-coming they sought to address was of mistaking a high degree of correlation for agreement (or concordance) between 2 measurement techniques.