I will present a detailed description of the analysis of quasi-static and Hopkinson bar data for a high-strength steel, HSLA 100. The purpose of the analysis is to determine the parameters for a Zerilli-Armstrong model that are suitable for a room-temperature, high strain-rate application. Furthermore, a thorough uncertainty analysis is required to be able to predict the uncertainties in simulations of the application scenario. This example may appear to be just a straightforward data-fitting problem, albeit a nonlinear one. On the other hand, because of disagreement between the data and the Z-A model, a number of decisions need to be made. Part of the solution to obtaining an acceptable result is to introduce systematic uncertainties to account for sample-to-sample variations in behavior. My purpose in presenting this material is to induce an open discussion of the various ways to cope with and estimate uncertainties in models derived from data.