Two classes of errors that may account for the theory-experiment gap are additive errors and proportional errors. An additive error does not scale with the property being measured; it is just a constant shift. For example, an uncalibrated scale with a container on it would always overestimate the weight of the object in the container by the same amount, regardless of the weight of the object. An equation of the form shown in equation 1 would be used to correct for this type of error, where P corrected is the corrected property value, P measured is the measured property value, and b additive is a constant correction factor, which would generally be fit to some calibration data where both P measured and a higher fidelity measurement of property P are known.