Experimentation Source 8 (Source)

Reference Documentation - Experimentation

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I believe the assembly part is a mirror image of the experimentation part. There's a formula for base chance for the assembly and an assembly roll. Since there are no clues there like the failure rate, it's much harder to find the formula. I suspect the base chance formula is based upon assembly skill, a resource stat and maybe the complexity. So far I don't think MA is used for assemblies, possibly OQ or maybe SR/UT.

Personally I find it a bit illogical that your assembly skill directly affects the experimentation roll. It's far more likely that it affects it indirectly by the assembly result. Either the assembly result gives a scaled bonus to experimentation roll for all types of assembly results or only for amazing assemblies. Like I mentioned above, amazing assemblies doesn't seem to do anything else, so my guess is on the second option.