This panel again is very similar to the Initial States Panel. The same division into selecting and editing applies. The editing window lists all reactions in the model. Each rate can be modified in the same manner as an initial concentration. Keep in mind that parameters are multiplicative: a uniform distribution between 1.0 and 2.0 applied to an association rate of 1.0e5 will result in a uniform distribution of rates between 1.0e5 and 2.0e5. The specifics how this distribution applied depend on the context in which it will be used. Rate parameters are often poorly constrained thus, you might want to vary a rate over a range spanning several order s of magnitude, in such cases the "Log Uniform" distibution comes handy. As the name suggestes, the distributions density is uniform in log scale. Therefore each decade will be sampled with approximately the same number of samples. In contrast a uniform distribution would usually drastically under-sample the lower decades. Consider for example a range from 0.01 to 100, and assume that 1000 samples will be drawn. Given a uniform distribution, on average, an interval of length 0.0999 would contain one sample. in other words the range 0.01 - 0.1 would be sampled with equal density as the range 99.001 - 100.