The cross-section sensitivity of the fusion probability has been calculated for various conditions of incident deuteron energy and plasma electron temperature. The fusion probability is most sensitive to the D-T cross section at the higher energies (≳50 keV), and, based on the reported errors in the cross section, the errors in the calculated fusion probabilities should be ≲10%. The cross-section sensitivities of the D-T reaction rate in a D-T plasma and the T-T reaction rate in a tritium plasma have also been calculated for various assumed values of the plasma ion temperature.