Statistics, Machine Learning, Data Science, Central Limit Theorem, Sample.
“sum of die rolls” = D_1 + D_2 maps from this state space to an integer in the range [2, 12]. Here, X is a mapping function: it has mappings from every possible combinations of two die rolls, to a number in [2, 12]. R.v. are basically lookup-tables. For US citizens the state-space is a bit complex,