# The Concurrent Validity of Mobile Application for Tracking Tennis Performance
## 3 Results  
The basic descriptive indicators (N, Mean, Min, Max, and St.Dev.) and validity parameters (ICCs) were calculated (Table 1) for the speed of the serve shot. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Variable** & **Instrument** & **N** & **Mean** & **Min** & **Max** & **St.Dev.** & **ICC** \\ \hline \multirow{2}{*}{**Speed\_DE**} & SV & 150 & 136.00 & 112.00 & 166.00 & 9.01 & \multirow{2}{*}{0.76} \\ \cline{2-6}  & Radar & 150 & 141.13 & 113.00 & 172.00 & 9.37 & \\ \hline \multirow{2}{*}{**Speed\_AD**} & SV & 150 & 141.24 & 108.00 & 180.00 & 10.43 & \multirow{2}{*}{0.80} \\ \cline{2-6}  & Radar & 150 & 145.60 & 102.00 & 191.00 & 10.32 & \\ \hline \hline \end{tabular} Speed\_DE—serve speed in deuce side of the court; Speed\_AD—serve speed in advantage side of the court; SV—software-gained data; N—number of serves; Mean—average value; Min—minimum value; Max—maximum value; St.Dev.—standard deviation; ICC—correlation between measurements.  
\end{table} 
Table 1: Basic descriptive indicators and measures of validity for speed variables of observed serve shots. Figure 4: In-app screenshot of performed serve with the illustration of court matrix and detection of serve placement along with serve speed. The mean values calculated for the shot's speed were highest when the serve shot was performed on the advantage side with radar measurement (145.60 km/h). Moreover, the highest (191.00 km/h) and lowest speed rates (102.00 km/h) were also recorded with the radar in Speed_AD. The lowest mean values of serve speed were determined in Speed_DE with SV. ICC values for speed validation were 0.76 for the deuce side and 0.80 for the advantage side of the court. [PERSON]'s \(\alpha\) coefficients were the same for both variables (0.86). The largest number of serves on both sides was played in Zone 4 (Table 2). Zone 4 presents missed serve, which on the AD side was (VA = 48%; SV = 44.67%) of the shots and on the DE side was 40% of all serves. On the advantage side, the application recorded fewer (67) missed serves than that found using video analysis (72). The largest number of serves was played in Zone 2, i.e., in the middle of the service box. A greater number of serves were played in Zone 3 than in Zone 1 when the subjects served from the deuce side, and vice versa when they served on the advantage side. ICC results determined good validity for both Place_DE (0.83) and Place_AD (0.87) variables. Table 3 shows the distribution of strokes according to their type. Forehand shots were played the most (VA = 44.80%/SV = 44.60%), while the next most common shot was backhand (VA = 28.60%/SV = 28.40%). A total of VA = 127/SV = 128 serve shots were played, which amounts to VA = 25.40%/SV = 25.60% of all the shots played. The lowest number of strokes was recorded in the game on the net (volleys and smash). Regarding the validity between video analysis and SwingVision, the ICC showed excellent validity (0.97). Video analysis and SV application recorded the highest number of topspin (VA = 46.80%/SV = 42.60%) and flat shots (VA = 34.80%/SV = 38.20%) (Table 4). The