Name:Khalid Saleh AL-Ghamdi Born on December, 1974. Dammam Saudi Arabia Career Experience: Lab scientist at Ras Tanura Petroleum Refinery Quality Control lab, Saudi Aramco Co. Since 2000 till today. Member of Royal Society of Chemistry, UK (MRSC). Part time PhD, student at the chemistry dep¿t at KFUPM University

This thesis work illustrates how statistical concepts such as; data analysis for their probability distribution modes, detection and treatment of data for the presence of outliers, regression analysis and multiple comparisons procedures (Tukey's, Dunnett, Fisher LSD ) can play a pivotal role in validating the performance of a modified standard method. Validating the performance of modified standard method is one of the requirements of the international ISO standards (ISO17025:General requirements for the competence of testing and calibration laboratories ). Practically, validation work could be a lengthy and labor intensive in some cases. So this thesis work represents a case study were a single laboratory validation was conducted with the help of using essential statistical concepts aforementioned. Moreover, this work is proposing an economical design of calibration practice for calibrating the lab equipment (Ion Chromatograph). The measurands considered into this study were; Fluoride, Chloride and Bromide in Naphtha matrix.