## 3 Results
### Validity
The gray-shaded region represents the confidence interval around the bias estimate. The green and red regions highlight the upper and lower bounds of agreement, respectively. The purple area (95% CI of the Mean Difference), represents the 95% confidence interval around the average difference (bias) between the two methods, indicating the precision of the estimated sys-tematic bias. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Bland–Altman**} & \multicolumn{3}{c}{**95\% Confidence Interval**} \\ \cline{2-4}  & **Estimate** & **Lower** & **Upper** \\ \hline Bias (n = 21) & 1.042 & 0.636 & 1.449 \\ Lower limit of agreement & \(-\)0.709 & \(-\)1.415 & \(-\)0.002 \\ Upper limit of agreement & 2.794 & 2.087 & 3.499 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Bland–Altman analysis for S] measurements: MyJump vs. Chronojump. To assess the relationship between squat jump (SJ) height measurements obtained using MyJump and Chronojump, a Pearson correlation analysis was also conducted (Table 5 and Figure 4). The results indicated a strong positive correlation (r = 0.955, \(p\) < 0.001), suggesting that MyJump provided highly comparable SJ height values to Chronojump, with a 95% confidence interval of 0.891-0.982. Additionally, [PERSON]'s rho (\(p\) = 0.961, \(p\) < 0.001) confirmed this strong relationship across both measurement tools. The scatter plot with regression fit (Figure 4) visually represented the correlation between MyJump and Chronojump for SJ. The tight clustering of data points along the regression line and the narrow confidence band indicated minimal variability and high measurement consistency between the two systems. The near-perfect correlation indicated that MyJump is a reliable alternative for measuring SJ performance. \begin{table}
\begin{tabular}{c c} \hline
**CMJ MyJump (cm)** & **CMJ Chronojump (cm)** \\ \hline Pearson’s r & 0.972 *** \\
95\% CI Upper & 0.989 \\
95\% CI Lower & 0.930 \\ [PERSON]’s \(\rho\) & 0.960 *** \\ \hline \end{tabular} Note. ***\(p\) < 0.001, CI = confidence interval.  
\end{table} 
Table 4: Correlation matrix between CMJ measurements from MyJump and Chronojump. Figure 2: Bland–Altman Plot: agreement between MyJump and Chronojump for squat jump (SJ) measurements. The x-axis represents the mean SJ height between the two methods, while the y-axis depicts the differences in SJ height (MyJump—Chronojump) for each trial. The blue line represents the mean bias (+1.042 cm), indicating that MyJump slightly overestimates jump height compared to Chronojump. The dotted lines mark the 95% limits of agreement (LoA), which range from \(-\)0.709 cm to +2.794 cm, defining the expected range within which most individual differences lie. The gray-shaded region represents the confidence interval around the bias estimate, while the green and red regions highlight the upper and lower bounds of the agreement range, respectively. The purple area (95% CI of the Mean Difference), represents the 95% confidence interval around the average difference (bias) between the two methods, indicating the precision of the estimated sys-tematic bias. The results of the linear regression analysis conducted to assess the predictive relationship between CMJ height measurements obtained using MyJump and Chronojump  
Figure 4: Scatter plot with Pearson correlation between SJ MyJump and Chronojump measurements (*** \(p<0.001\)). \begin{table}
\begin{tabular}{c c} \hline \hline
**CMJ MyJump (cm)** & **CMJ Chronojump (cm)** \\ \hline [PERSON]’s \(r\) & 0.955 *** \\
95\% CI Upper & 0.982 \\
95\% CI Lower & 0.891 \\ [PERSON]’s \(p\) & 0.961 *** \\ \hline \hline \end{tabular} Note. *** \(p<0.001\), CI = confidence interval.  
\end{table} 
Table 5: Correlation matrix between SJ measurements from MyJump and Chronojump. Figure 3: Scatter plot with Pearson correlation between CMJ MyJump and Chronojump measurements (*** \(p<0.001\)).