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Metrological traceability is defined as the property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty. A reference is a measurement unit including its practical realization. Unsupported air dielectric coaxial transmission lines (or air lines) have been used as primary reference standards for impedance measurements at RF and microwave frequencies. Multi-line Line-reflect-line (LRL) calibration kits are used to achieve the very highest levels of accuracy required by metrology labs. By analyzing the measurement risks from different VNA calibration schemes, users can demonstrate the adequacy of uncertainty budgets, which is a requirement for mitigation of measurement risk and demonstration of traceability. A comparison of automatic calibration vs. LRL will be used as the case study for measurement risk.