###### Abstract
Firstly, the Si coating was deposited for 0.5 h (used saline SiH\({}_{4}\)) to improve adhesion of the DLC coating (used C\({}_{2}\)H\({}_{2}\)), which was subsequently deposited for 2 h. The technological parameters of the deposition process were constant: pressure ranging from 5 mTorr to 70 mTorr; bias from 350 V to 650 V; gas flow of 5 cm\({}^{3}\)/min; length of an impulse equal to 15 \(\upmu\)s; and frequency equal to 21 kHz. The thickness of the DLC coating has decreased in a linear manner from 0.75 \(\upmu\)m (the start of the cylinder) to 0.05 \(\upmu\)m (the end of the cylinder) [8]. Precursors did flow through the tube, always in one direction. [PERSON] et al. [9] deposited the DLC coating on the inner surface with a diameter equal to 3 cm and a length equal to 40 cm. They evaluated the thickness and hardness of the coatings. They also changed the frequency of the power supply. At 0.1 kHz, an equal thickness of ca. 5 \(\upmu\)m [9] was achieved. [PERSON] et al. [10] used plasma immersion ion implantation into a cylindrical bore. The tube had an inner radius equal to 4.8 cm and a length equal to 20 cm. [PERSON] et al. [11] used an arc-evaporated Ti and a N\({}_{2}\) reactive gas for the deposition of a TiN PVD coating on the inner surface of a steel tube. The thickness of the coating changed from 2.3 \(\upmu\)m (in the center of the tube) to 2.7 \(\upmu\)m (at the ends of the tube). The tube did rotate around an axis perpendicular to the axis of the tube during the TiN coatings' deposition. [PERSON] et al. [12] and [PERSON] et al. [13] used an electric arc to melt Ti and N\({}_{2}\) gas for the TiN PVD coatings' deposition on the inner surface of the steel tube. Regression analysis and correlation analysis are statistical methods generally commonly used to evaluate and assess the results of experimental measurements. These methods are used by many authors in their works, which are devoted to the coating of various materials. [PERSON] et al. [14] used them in the evaluation of the plasma spray coating process. Regression equations for the prediction of adhesion of sprayed coatings were used by [PERSON] et al. [15]. To estimate the critical load for the adhesion of 75% WC-Co + 25% Ni alloy by plasma spraying, statistical analysis was used in the paper [16]. To determine the weight of the coating, the multiple regression method was successfully applied in the work [17]. Regression analysis is used in [18] to investigate the coating process aimed at protecting the photolithographic matrix from silicon contamination. The accuracy of neural network predictions is compared with regression analysis in the design and development of shielded fluxes for depositing electrode coatings for arc welding [19; 20]. [PERSON] et al. [21] investigated the chemical composition of coatings from quaternary metal oxides RuIrSnLa deposited on Ti. The relationship between process input parameters and output response sensitivity analysis was investigated in the work of authors [PERSON] et al. [22]. [PERSON] and [PERSON] [23] investigated the physicochemical and thermophysical characteristics of deposited coatings and developed a regression model. In [24], the authors, [PERSON] et al., monitored the coatings using electrochemical impedance spectroscopy. Among other things, they used regression procedures to evaluate the data. The creation of thin layers is a complex process that has an impact on the properties of the layer. The aim of this article is to use appropriate statistical methods (statistical hypothesis testing, ANOVA method, regression, and correlation analysis) to determine the dependence of the observed variables (angle of grain growth, thickness of the deposited layer, adhesion in the direction of grain growth, adhesion against the direction of grain growth, roughness of the deposited layer) on the selected input variables (height of the measured location above the target and radius of the tube) when depositing the Ti layer by the EB PVD method.