The total error approach is a statistical technique for assessing performance of analytical methods. It could be used for any lab data analysis in oncology or other clinical trials or for the testing of new drugs. Due to variable parameters involved in inter-laboratory transfer of clinical trials like analysts, instruments, day/sessions and geographic location, there are chances of different assignable and non-assignable causes of variations. Here, the statistical analysis of measurement processes helps to identify and quantify sources of variation. The total error approach evaluates the variability in the parameters and helps the scientist in decision making.