Tamaki et al. (2005) stated that it is necessary to show the numerical targets to improve sports skills. In volleyball, Miyakozawa et al. (1982) indicated the standard values dividing the winning and losing with Break Even Point. However, this study showed the values at 50% probability of win/loss. We need the percentage of winning and losing that are more clearly divided. The present study is to develop achievement standards and the item difficulties in volleyball with decision tree analysis and item response theory. The results could be applicable in practical coaching situations. The data were collected from the Kyushu University Women's Volleyball League (University Women) of 2018 and the V.LEAGUE Women's Division 1 (V-League) of 2018-19. As a result, the number of serve points (1.5 times), block points (2.5 times), and successful reception rate (AB) (74.1%) of the V-League were higher than that of University women. The item difficulties of the number of attack points were low in both categories (V-League: -1.464, University women: -0.486). It suggested that those were easy to achieve. Although the number of attack points was assumed to contribute to the winning of the match (Minowa and Yoshida, 1990), those were easy to achieve. It is concluded that scoring from serves and blocks may affect the strength of the team.
