## 3 Results  
The factor analysis of the four Stroop variables resulted in the extraction of one significant principal component (Factor 1), explaining 83% of the total variance. The On \(-\) OffT had the lowest correlation with the principal component (r = \(-\)0.79), followed by OffT (r = \(-\)0.85). OnT and Off + OnT had the highest correlation with principal component (both r = \(-\)0.99). The extracted factor is defined as psychomotor speed and will be addressed in further text as PSM variable (Table 2).  
When multiple regression was performed for TRAG in the validation subsample of boys, the predictors accounted for 80% of the variance in the criterion. Significant partial regressors included T_CODS (\(\beta\) = 0.53) and SJ (\(\beta\) = \(-\)1.01). The regression model for TRAG obtained in the validation subsamples was as follows: TRAG = 2.11 + 0.65 \(\times\) TCODS \(-\) 0.10 \(\times\) SJ + 0.06 \(\times\) DJH + 0.13 \(\times\) 20Y BP. Upon applying the regression model to the cross-validation subsample, a common variance of 44% (\(p\) < 0.05) was observed between the calculated and observed scores. In the subsequent phase, a comparison of the calculated and observed scores for TRAG revealed no significant difference in the cross-validation subsample (3.37 \(\pm\) 0.49 and 3.29 \(\pm\) 0.35, \(p\) = 0.43; respectively). This confirmed the appropriateness of the regression modeling for TRAG in boys (Table 3).  
When multiple regression was performed for TRAG in the validation subsample of girls, the predictors accounted for 43% of the variance in the criterion. The significant partial regressor was CODS (\(\beta\) = 0.65). The regression model for TRAG obtained in the validation subsamples was as follows: TRAG = 1.42 + 0.78 \(\times\) TCODS. Upon applying the regression model to the cross-validation subsample, a common variance of 42% (\(p\) < 0.05) was observed between the calculated and observed scores. The calculated and observed scores for TRAG were compared using a t-test for dependent samples. No significant difference was found between the calculated and observed scores for the cross-validation subsample (3.70 \(\pm\) 0.30 and 3.68 \(\pm\) 0.40, \(p\) = 0.81, respectively). This confirmed the appropriateness of the regression modeling for TRAG in girls (Table 4).  
\begin{table}
\begin{tabular}{c c} \hline
**Variable** & **Factor 1** \\ \hline OffT & \(-\)0.85 \\ OnT & \(-\)0.99 \\ Off + OnT & \(-\)0.99 \\ On \(-\) OffT & \(-\)0.79 \\ \hline \end{tabular} Legend: OffT\(-\)psychomotor ability. OnT\(-\)response inhibition and motor speed, Off + OnT\(-\)composition measure of psychomotor speed and response inhibition, On \(-\) OffT\(-\)psychomotor speed.  
\end{table}
Table 2: Factorial structure of psychomotor variables in the Stroop test.  
\begin{table}
\begin{tabular}{c c c c c c} \hline  & \(\beta\) & **SE (\(\beta\))** & **b** & **SE (b)** & **t-Value** & \(p\)**-Value** \\ \hline Intercept & & & 2.11 & 0.73 & 2.89 & 0.01 * \\ TCODS & 0.53 & 0.14 & 0.65 & 0.17 & 3.80 & 0.00 * \\ SJ & \(-\)1.01 & 0.31 & \(-\)0.10 & 0.03 & \(-\)3.30 & 0.01 * \\ DJH & 0.63 & 0.31 & 0.06 & 0.03 & 2.01 & 0.07 \\
20Y BP & 0.20 & 0.16 & 0.13 & 0.10 & 1.27 & 0.23 \\ R & 0.90 & & & & \\ R\({}^{2}\) & 0.80 & & & & \\ \(p\) & 0.001 & & & & \\ \hline \end{tabular} Legend: TCODS—triangle test change of direction speed, SJ—squat jump, DJH—drop jump height, 20Y BP—20 yard BlazePod, \(\beta\)—regression coefficient, SE (\(\beta\))—standard error of the regression coefficient, * indicates the statistical significance of \(p\) < 0.05.  
\end{table}
Table 3: Forward stepwise linear regression of TRAG was conducted for the validation sample, separately for boys.