## 3 Results and Discussion
### Statistical Analysis of the Results  
Based on the deviation plots shown in Figures 6-9, determined by the optical method, and Figures 11-14, determined by the contact method, we created diagrams with statistical plots (Figures 15 and 16) and a table containing the corresponding values (Table 4). In the diagrams below, positive values for machined surfaces (MSs) indicate material gain while negative values for the bottoms of the samples (BOFs) indicate material loss. There is a symmetric distribution of deviations with respect to the horizontal axis y = 0. Figure 14: Dimensional variation of the horizontal thin wall in the direction perpendicular to the direction of tool feed motion, for samples made of nickel alloy machined using an adaptive face milling strategy—determined by the contact method: (**a**) N4; (**b**) N5; (**c**) N6. Figure 16: Statistical results of dimensional variations determined by the contact method. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Method**} & **Sample** & **Mean** & **Median** & **Minimum** & **Maximum** & **Variance** & **Standard** & **Standard** \\  & **Number** & **Value** & **Value** & **Value** & **Value** & **Value** & **Deviation** & **Error** \\ \hline \multirow{9}{*}{Optical} & N1\_MS & 0.20 & 0.22 & \(-\)0.02 & 0.28 & 0.00 & 0.07 & 0.01 \\  & N1\_BoF & \(-\)0.18 & \(-\)0.20 & \(-\)0.25 & 0.00 & 0.00 & 0.06 & 0.01 \\  & N2\_MS & 0.22 & 0.23 & \(-\)0.05 & 0.35 & 0.01 & 0.10 & 0.01 \\  & N2\_BoF & \(-\)0.28 & \(-\)0.31 & \(-\)0.41 & 0.06 & 0.01 & 0.11 & 0.01 \\  & N3\_MS & 0.44 & 0.45 & 0.16 & 0.58 & 0.01 & 0.11 & 0.01 \\  & N3\_BoF & \(-\)0.39 & \(-\)0.40 & \(-\)0.52 & \(-\)0.11 & 0.01 & 0.11 & 0.01 \\  & N4\_MS & 0.22 & 0.23 & 0.02 & 0.31 & 0.00 & 0.07 & 0.01 \\  & N4\_BoF & \(-\)0.26 & \(-\)0.26 & \(-\)0.34 & \(-\)0.08 & 0.00 & 0.06 & 0.01 \\  & N5\_MS & 0.13 & 0.14 & \(-\)0.06 & 0.22 & 0.00 & 0.07 & 0.01 \\  & N5\_BoF & \(-\)0.24 & \(-\)0.26 & \(-\)0.33 & \(-\)0.04 & 0.00 & 0.07 & 0.01 \\  & N6\_MS & 0.22 & 0.22 & 0.09 & 0.30 & 0.00 & 0.05 & 0.00 \\  & N6\_BoF & \(-\)0.18 & \(-\)0.19 & \(-\)0.26 & \(-\)0.05 & 0.00 & 0.05 & 0.01 \\ \hline \multirow{2}{*}{Contact} & N1\_MS & 0.20 & 0.22 & \(-\)0.01 & 0.29 & 0.01 & 0.07 & 0.01 \\  & N1\_BoF & \(-\)0.18 & \(-\)0.20 & \(-\)0.26 & 0.01 & 0.00 & 0.07 & 0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of statistical results of dimensional variation. Figure 15: Statistical results of dimensional variations determined by the optical method. Using the minimum and maximum values of thin wall deviations in Table 4, we calculated the maximum differences between the optical and contact methods results on the machined surfaces--MSs (Table 5) and at the bottoms of the samples--BOFs (Table 6). We see in Tables 5 and 6 that the maximum differences between the values obtained by the optical and contact methods are approximately 8%. [PERSON] and coworkers [28] reported a smaller value of 5%. On the basis of the box-plots in Figures 14 and 15 and the descriptive statistics in Table 4, we formulated the following conclusions:  
* The use of an adaptive cylindrical milling strategy (N4-N6) results in less scatter between the values obtained than the use of the adaptive face milling strategy (N1-N3). * Similar average values of the dimensional variations are observed for samples machined with the tool for general purpose (N1 and N4). A larger scatter of results appears for samples made with the other tools (N2, N3, N5, N6). * The largest average value pertains to the N3 sample (the tool for high-speed machining, adaptive face milling). * The smallest average is seen for the N5 sample (the tool for high-performance machining, adaptive cylindrical milling), while the N1 sample (the tool for general purpose, adaptive face milling) has the lowest maximum deviation. * Sample N6 milled with the tool for high-performance machining and using adaptive cylindrical milling has the smallest difference between the minimum and maximum.