Abstract
BACKGROUND: This study analyzed how Video Assistant Referee (VAR), introduced to improve the accuracy of referee decisions in football, changes the magnitude and direction of home advantage and referee bias in the Turkish Super League. METHODS: We analyzed points, goals, yellow cards and red cards, fouls, penalties, and offside data from 1,838 matches played in the Turkish Super League with and without VAR. Two-sample t-tests and two one-sided tests analysis were applied to determine the differences between the home and away team data between the seasons played with and without VAR. RESULTS: The findings revealed that the only variable that changed significantly after VAR was implemented was fouls, which decreased for both home (p <.001; d = 0.56, medium effect) and away teams (p <.001; d = 0.69, medium effect). The results also indicated that, with or without VAR, home teams had an advantage over away teams in points and goals, and away teams faced more referee bias regarding yellow cards and penalties (against). CONCLUSIONS: Although this study shows that VAR does not significantly impact the HA and referee bias of football matches, nevertheless, teams should be more aware that bias is reduced when playing away. In addition, this study offers some practical applications that can help football players, coaches, and match officials better understand VAR technology's effects on HA and referee bias.