A New Diagnostic for MOND Fits in SPARC Galaxies: TheVbar/Vflat Ratio

We present a systematic chi-squared analysis of the full SPARC sample of 175 late-type galaxies(3,391 rotation curve data points), comparing four physically motivated models: MOND and threedark matter halo profiles (NFW, Isothermal, Burkert). Using chi-squared per degree of freedom(chi2_red) and the corrected Akaike Information Criterion (AICc) as primary statistics, we find: (A)Cored isothermal profiles are preferred over cuspy NFW in 100 vs. 15 galaxies by decisive AICc (|ΔAICc|>2); Wilcoxon p = 9.3×10 ¹⁹. (B) MOND achieves chi2_red < 2.0 in 28.6% (50/175) of ⁻galaxies; median R² = 0.732. (C) We introduce V_bar/V_flat as a novel model-free MOND diagnostic:logistic regression predicts MOND fit quality with 71.4% accuracy (AUC = 0.649; 10-fold CV0.714±0.008; threshold 0.194). (D) The Radial Acceleration Relation is confirmed: Pearson r = 0.9576,σ = 0.163 dex, N = 3,391. (E) BTFR slope from stellar population synthesis masses = 3.813 ± 0.084,2.2σ from MOND (4.0). Comparison against EAGLE, IllustrisTNG, SIMBA, and FIRE-2 indicatestension with standard ΛCDM, subject to the caveat that this comparison is not selection-functionmatched. All results derive from published SPARC data without modification.