What’s the difference between Stat 100/102/104 and Stat 110?

They are complementary, with very little overlap. Stat 100, 102, and 104 are each an introduction to statistical principles and concepts, as described above. Stat 110 is an introduction to probability. The emphasis of Stat 110 is on random variables and their distributions, and on how to use probability to quantify uncertainty and understand randomness. Aside from the very different emphasis, Stat 110 is taught at a much higher mathematical level than Stat 100/102/104. In particular, Stat 110 requires calculus at the level of Math 1a/1b or above.