In this analysis, (actual SENS.SCP file), after running a reference simulation, each parameter
      is perturbed and another analysis is run. For each measurement
      vector, the difference between the reference and the perturbed
      result, the sensitivity, is saved. This results in a number of
      simulations equal to the number of parameters that have tolerances.
      As a matter of convention, each tolerance
      is taken as the 3 sigma value, or 3 standard deviations and we
      report the Sensitivity results as though they were also 3 sigma.
      The sensitivities for each parameter are reported for all measured
      vectors in descending order of magnitude in the IsSpice4 output
      file. The sensitivities can be tabulated for each measured vector
      or for each parameter.