Initial Data for SPICE Monte Carlo Simulations

GRO Compiler

How do we get the results for SPICE Monte Carlo simulations when we haven't run any actual tests before? In other words, say I don't have any of the physical components built yet and I haven't measured any data, but I want to run the SPICE Monte Carlo simulations. In this case, what do the simulations base their initial data off of? Can bad initial data affect anything down the production line?