## 3 Results
### Results of Statistical Analysis--Bias-Ply Tire  
Table 7 presents the results of the multivariate analysis of variance for the results obtained for the bias-ply tires. The \(p\)-values presented represent the level of probability of accepting the null hypothesis stating that there is no significant impact of the factor on the analyzed parameter. It can be concluded that in most cases, both factors had a significant impact on the analyzed parameters because the \(p\)-values were much lower than the significance level \(\alpha\). The only exception was the influence of inflation pressure on the tire cross-section value--in this case, the statistical analysis did not show any significant differences. As a part of the analysis, post hoc tests were also performed to indicate between which factor levels there were significant differences. In the case of the first factor (vertical load), there were only two levels (11.8 kN and 19.6 kN), so if the analysis showed a significant effect, it meant that there must have been significant differences between the two levels. However, \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Footprint Parameter** & **Factor** & **Factor Level** & **Arithmetic Mean** & \(\pm\)**SD** & \(p\)**-Value** \\ \hline \multirow{4}{*}{Width of the footprint, mm} & \multirow{2}{*}{Vertical load} & 11.8 kN & 444.87 \({}^{\text{A}}\) & 7.99 & \multirow{4}{*}{0.00001} \\ \cline{3-3}  & & 19.6 kN & 462.12 \({}^{\text{B}}\) & 12.31 & \\ \cline{3-3}  & & 0.08 MPa & 465.75 \({}^{\text{A}}\) & 13.33 & \\ \cline{3-3}  & Inflation & 0.16 MPa & 449.69 \({}^{\text{B}}\) & 10.20 & 0.000004 \\ \cline{3-3}  & pressure & 0.24 MPa & 444.92 \({}^{\text{B}}\) & 6.86 & \\ \hline \multirow{4}{*}{Length of the footprint, mm} & \multirow{2}{*}{Vertical load} & 11.8 kN & 476.09 \({}^{\text{A}}\) & 5.33 & \multirow{4}{*}{0.000015} \\ \cline{3-3}  & & 19.6 kN & 500.90 \({}^{\text{B}}\) & 14.52 & \\ \cline{3-3}  & & 0.08 MPa & 497.03 \({}^{\text{A}}\) & 14.04 & \\ \cline{3-3}  & Inflation & 0.16 MPa & 479.02 \({}^{\text{B}}\) & 8.65 & \\ \cline{3-3}  & pressure & 0.24 MPa & 489.44 \({}^{\text{A}}\) & 9.37 & \\ \hline \multirow{4}{*}{Depth of the footprint, mm} & \multirow{2}{*}{Vertical load} & 11.8 kN & 24.80 \({}^{\text{A}}\) & 0.87 & \multirow{4}{*}{0.00006} \\ \cline{3-3}  & & 19.6 kN & 30.72 \({}^{\text{B}}\) & 1.01 & \\ \cline{3-3}  & & 0.08 MPa & 15.94 \({}^{\text{A}}\) & 2.85 & \\ \cline{3-3}  & Inflation & 0.16 MPa & 30.51 \({}^{\text{B}}\) & 1.49 & \\ \cline{3-3}  & pressure & 0.24 MPa & 36.83 \({}^{\text{C}}\) & 3.48 & \\ \hline \multirow{4}{*}{Cross-section area of the tire, m\({}^{2}\)} & \multirow{2}{*}{Vertical load} & 11.8 kN & 0.179 \({}^{\text{A}}\) & 0.019 & \multirow{4}{*}{0.000006} \\ \cline{3-3}  & & 19.6 kN & 0.217 \({}^{\text{B}}\) & 0.019 & \\ \cline{3-3}  & & 0.08 MPa & 0.199 \({}^{\text{A}}\) & 0.034 & \\ \cline{3-3}  & Inflation & 0.16 MPa & 0.194 \({}^{\text{A}}\) & 0.009 & \\ \cline{3-3}  & pressure & 0.24 MPa & 0.202 \({}^{\text{A}}\) & 0.017 & \\ \hline \multirow{4}{*}{Tire–soil contact area, m\({}^{2}\)} & \multirow{2}{*}{Vertical load} & 11.8 kN & 0.220 \({}^{\text{A}}\) & 0.018 & \multirow{4}{*}{0.000002} \\ \cline{3-3}  & & 19.6 kN & 0.266 \({}^{\text{B}}\) & 0.019 & \\ \cline{3-3}  & & 0.08 MPa & 0.232 \({}^{\text{A}}\) & 0.037 & \\ \cline{3-3}  & Inflation & 0.16 MPa & 0.234 \({}^{\text{A}}\) & 0.010 & 0.000828 \\ \cline{3-3}  & pressure & 0.24 MPa & 0.263 \({}^{\text{B}}\) & 0.027 & \\ \hline \end{tabular}  
* The letters at arithmetic means (\({}^{\text{A,B,C}}\)) denote separate homogenous groups.  
\end{table} 
Table 7: Results of the statistical analysis of experimental data for the bias-ply tire; the significance level \(\alpha=0.05\); SD—standard deviation. the second factor (inflation pressure) had three levels, so it was justified to perform a homogeneous group test. It showed that only for the footprint depth, each pressure level was a separate, homogeneous group (there were significant differences in the footprint depth values between each of the inflation pressures).