Measurement of Uncertainty is the extent of doubt in a measurement. For instance a weighing balance showing 1 Kg may not be exactly 1 Kg but may be slightly more or less. The doubt extends to all measurements, be it weight, distance, volume etc. In a laboratory during testing the composition for a sample of mineral, several measurements come into play. Each of these measurement s contribute to an uncertainty or doubt and that is represented for each analysis. Statistical analysis is used to compile all the uncertainty for all the processes and expressed as a value +/- (uncertainty value). For example total Fe in iron ore could be 63.4 +/- 0.32 where 0.32 is the uncertainty value applicable for that lab. These days the measurement of uncertainty has assumed great importance and it is mandatory for a laboratory to express its value of uncertainty for each sample and each parameter. Every lab therefore must conduct repeatability, reproducibility tests for each parameter tested. All equipments and glass ware need calibration, raw material need to be quality checked and training of chemists done regularly to gauge competence in order for the lab to possess a lower uncertainty of measurement (UM). MSK has been focusing on this aspect and it recently conducted a work shop with its customer service teams to impart better understanding on this subject.