The theme of this work is defining qualitative variables taking into account their measurement properties, and providing a systematic overview of the methods for describing and defining these variables. As each process is defined by the influence of quantitative, but also qualitative parameters, it is important to study the methods for performing statistical testing of these variables. A general description of qualitative variables, not limited to engineering areas, is given in the first chapter. There are three main characteristics defining this kind of variables and a common method of collecting them. The second chapter is about defining statistical variables, their division and characteristics of each type. The next step was to demonstrate the methods of analyzing qualitative data and the way they are displayed depending on the the type of each individual variable. The core of this paper is to analyze the methods of planning experiments, their origin and application from an engineering aspect. Different concepts that provide a base for this very important method of analysing influential parameters in individual processes are explained. The steps for planning, conducting and finally analysing an experiment are also defined, as well as the principles of blocking undesirable influencing factors. The focus of the study was on multifactorial designs, particularly the one that provides analysis of parameters with only two levels, the 2k factorial design. The steps for performing a mathematical analysis of cells underlying these designs were given. It was important to specify the methods used to determine into which blocks certain factors belong. It was necessary to explain the above mentioned methods on a real example. Using a set of data about the measurements of an aluminium cylinder, more specifically about its inner and outer diameter and length, a design of an experiment was carried out in order to determine the potential influence of parameters when measuring these quantities. A statistical analysis of three parameters was also carried out. It resulted in a few conclusions about the significance of each factor.