The quality of results from a molecular dynamics (MD) simulation is determined by the accuracy of interatomic forces. Often interatomic forces are determined using quantum mechanical methods such as density functional theory (DFT). However, we have previously shown that DFT will not always produce accurate forces. Presumably errors in the forces from DFT will cause errors in MD results, but the sensitivity has not been quantified. In this work, we focus on how the thermal conductivity changes with respect to the interatomic forces. Direct exploration of changes in thermal conductivity by varying parameters for the DFT calculations (and thus the forces) would be very expensive, but we can extract this sensitivity indirectly using classical MD with the Tersoff potential for diamond-cubic silicon. We have found that the percent change in thermal conductivity of silicon is 0.56 times the percent change in average force magnitude, which provides a useful metric for estimating errors in thermal conductivity resulting from errors in interatomic forces. We expect the results to generalize to other materials and potentials.