Many material properties are calculated using density functional theory (DFT), but there always exists some difference between the DFT and experimental values. Modeling this error can help calibrate DFT results and make them more accurate. For example, the formation energy of crystal structures calculated using DFT are imperfect, and they are often corrected to more closely match experimental values. There is a set of about 1500 calorimetry experiments, published by Kingsbury et. al., for which both the experimental formation energy and the crystal structure are believed to be known. Figure clearly shows that there is a difference between theory and experiment, and applying a calibration, or "correction," would be a sensible way to improve the accuracy of DFT-calculated formation energies. In this work, we will discuss two classes of errors, how each can be modeled, and the benefits and drawbacks of accounting for each type of error.