IMPLEMENTING Z-SCORES AS A METHOD OF DISTINGUISHING BETWEEN WINNING AND LOSING IN RUGBY UNION WITHIN THE WELSH PRINCIPLAITY PREMIERSHIP

Abstract

The aim of this study was to construct an effective method for statistical analysis of individual and team performance within semi-professional Rugby Union teams, to produce normative values for performance and to provide useful and practical data for a coaching setup on a game by game analysis. The sample consisted of 30 games, 10 which were used to analysed team key performance indicators (KPI’s) and 20 which were used to analysed individual KPI’s from the Welsh Principality Premiership. The means and standard deviations for the overall value of each KPI for the team coding were calculated. The means and standard deviations were then calculated for both the winning and losing performances separately, these values were then used to calculated Z-Scores for each KPI for winning and losing performance on each game. A two related variables Wilcoxon test was performed to highlight the team related KPI’s that significantly differ between winning and losing teams. The statistical test revealed that five out of the twenty team KPI’s differed significantly, namely tries (0.027), conversions (0.019), kicks infield (0.049), kicks bounce to touch (0.046) and turnovers total (0.050). Z-scores were then utilised on each game to emphasise how they can effectively present differences between the KPI’s that contribute to winning and losing team in a graph format. Coaches can use this relatively unutilised form of results to bring attention to areas of performance that have performed poorly, to inform the training sessions in preparation for future games. Moreover this study has shown that there are many different KPI’s that distinguish between winning and losing performance, but they are subject to chance dependent on factors such as opposition effect, match venue etc, from game to game. This is hugely important for a coach to understand in order to maintain successful performance over a series of games.