The thesis “Improvement of the welding process of refrigeration circuit for domes-tic appliances: Haier Europe’s case study” has been developed during my entire internship period in the headquarter of Haier Europe, based in Brugherio (Milan). The activities developed during the internship period as a quality data analyst in the Cooling business sector, can be summarized according to these activities: the acquisition of raw data and the subsequent cleaning of them for the realization of a reliable analysis of the quality trend for all refrigeration products. The headquarter environment is very dynamic, where the business of all the mar-ket are managed and monitored, particularly in the Haier Europe organization, where all the activities carried out by all the business sectors are driven by an unique focus: the customer satisfaction.