A tale of two selection biases: The independent effects of relative age and biological maturity on player selection in the Football Association of Ireland's national talent pathway

This study investigated the associations between biological maturation status (classified using Khamis–Roche method for percentage of predicted adult height at time observation) and relative age (expressed as a decimal value to difference birth date competition cut-off date) extent which their selection biases existed across competitive groups in an analysis players within Football Association Ireland's (FAI) national talent pathway. The assessed were either from U13 FAI National Academy ( n = 125), Ireland U15 team 18), or U16 16). A moderate very large bias favour early maturing was observed all groups, increasing magnitude with successive p < 0.05). total 46–72% selected into pathway maturing; 0% late maturing. effect cohorts 0.05), although not chronological smaller than biases. small positive correlation absolute maturity observed, inverse 0.01) observed. There no other significant correlations age. We encourage Associations critically reflect upon criteria squad selection; current system diminishes chances players.