This paper presents a stability analysis of the sensor data which is collected by QTAGG from alarge ocean going ship and using the stability results, introduces some information about howthe measurements that come from the sensors can be improved and how reliable they are. In thetheoretical part, some background information is given mainly based on British Standard(BS)ISO 19030 which was published in November, 2016. This source basically includes someinformation about the measurement of changes in hull and propeller performance of a vessel.Using the theoretical information, in the implementation part, the necessary methods areimplemented in python programming language on a real life data set of a vessel which is givenfrom QTAGG company. To measure the stability of the parameters in the data, we loosenthe filters of the parameters and observe how they respond to the technical changes. In orderto understand how loosen the filters can be made, a reference speed-power curve is createdby using a curve fitting method, and after creating a performance indicator by utilizing thereference curve, Anderson-Darling and Shapiro-Wilk tests are used to measure the stability ofthe performance indicator. Besides these numerical tests, some visual methods such as Q-Qplot and histogram plot are also used in this process. Finally, we could provide stability resultsby using both our theoretical knowledge and the practical implementation.