I have a question about stochastic user equilibrium assignment in TransCAD. There are two options for the error distribution: normal and gumbel. In addition, one has to specify the variance of the error distribution. The default value is "Error=5". I don't know what this "Error=5" refers to. Is it the standard deviation or the variance (for the normal function)? Is it the standard deviation, the variance or the parameter of the gumbel function (for the gumbel function)? I've looked it up in TransCAD manual, but I haven't found any specific information.