σ_gt/μ_gt take only finitely many distinct values because of the GT image's 8-bit quantization -- that property itself is correct.However, the specific figures reported in Technical Reports v1.16/v1.18/v1.19 (approximately 2.3 million distinct values for σ_gt, 68,649 for μ_gt) turn out to have been inflated by about 1.95x and 4.2x respectively, due to a separate issue unrelated to quantization: floating-point addition's non-associativity producing "ghost duplication" (the same true value recorded as slightly different bit patterns depending on the exact computation path). This report demonstrates the mechanism behind this phenomenon with concrete examples, and presents a higher-precision pipeline -- tolerance-based adjacent-gap analysis (the "LAG method") -- for computing the true, quantization-derived distinct-value count (σ_gt≈1.18 million, μ_gt≈16,320), confirmed byte-for-byte identical across all 4 models. Includes 10 verification SQL scripts, 10 execution videos, 2 Python DB-construction scripts, and hashes for everything (24 files in total). CC BY-NC 4.0. Dataset and Mandatory Citation: - Source: NIH ChestX-ray8 (Hospital-scale chest x-ray database) - Citation: Wang, X., Peng, Y., Lu, L., Lu, Z., Bagheri, M., & Summers, R. M. (2017). "ChestX-ray8: Hospital-scale chest x-ray database and benchmarks on weakly-supervised classification and localization of common thoracic diseases." Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 3462–3471. - Download: https://nihcc.app.box.com/v/ChestXray-NIHCC Contact: s.shiny.n.works@gmail.com (individual) /n.mohumohu@merit-metrics.org (Meritcs) Published by Meritcs (https://merit-metrics.org), an independentresearch organization studying image-quality metric reliability.
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neco mohumohu (2026) studied this question.