Figure 2. The visible evaluation model of the tactical benefit of the first to third strokes in the service round. The median tactical frequency and scoring rate in the tactics of the first to third strokes are 0.031 and 0.481, respectively. Therefore, the tactical benefit value ranges of the four areas are (0.058, 5]; (0, 0.058]; [-0.058, 0) and [-5, -0.058), respectively.