Table 7.

Cross-stratum robustness profile of the fusion model

Stratification axis	Subgroup	Sample N	Fusion accuracy (%)	Δ (pp)
Per-sport (LOSO)	Basketball Dribbling	980	85.9 ± 1.4	−3.3
	Standing Long Jump	980	90.4 ± 1.1	−3.4
	Sit-ups	980	87.6 ± 1.2	−2.9
	50 m Sprint	980	88.5 ± 1.3	−3.2
Gender (within-domain)	Boys	2,100	91.4 ± 0.5	+ 0.1
	Girls	1,820	91.2 ± 0.5	−0.1
Age (within-domain)	13 years	1,240	90.9 ± 0.5	−0.4
	14 years	1,420	91.5 ± 0.4	+ 0.2
	15 years	1,260	91.6 ± 0.5	+ 0.3
Baseline skill (within-domain)	Low tertile (0–5.5)	1,310	89.4 ± 0.7	−1.9
	Mid tertile (5.5–7.5)	1,300	91.4 ± 0.5	+ 0.1
	High tertile (7.5–10)	1,310	92.4 ± 0.4	+ 1.1

Per-sport LOSO accuracies are averaged across the three held-out schools; cross-gender, cross-age, and cross-baseline-skill accuracies are computed within the standard participant-wise split (within-domain) using out-of-fold predictions from the five-fold internal cross-validation described in Sect.  "Classification accuracy analysis". 

All values are mean ± SD over ten random seeds. Δ is computed against the corresponding within-domain per-sport accuracy (Fig. 3) for per-sport LOSO rows, and against the overall within-domain headline of 91.3% for within-domain stratum rows