Proficiency test (PT) is an important way of meeting the requirements of NABL accreditation (ISO/IEC 17025) in the areas of chemical testing. It provides laboratories with
an objective means of assessing and demonstrating the reliability of data they produce. In this study, 18 laboratories interested in the ultimate analysis of coal participated in a proficiency test conducted by CSIR-National Metallurgical Laboratory, Jamshedpur in collaboration with CSIR-National Physical Laboratory, New Delhi in 2011-12. The participating Iaboratories used classical and instrumental methods of analysis to determine moisture, ash, volatile matter and total sulfur in a homogenized coal sample. This paper reports the analytical results and statistical evaluation of the results using z-score
