Consider a simplified pachinko-like pinball machine: drop a ball at the top of the pyramid, and give it a 50-50 chance of ricocheting left or right as it descends. By the time it gets to the bottom it likely will be somewhere near the middle – but not always. This LOOPY model simulates the situation. As the lines on the "Variable Dynamics" graph show, probability starts out concentrated in the center and diffuses outward to form a Pascal's Triangle shape, 1-4-6-4-1 in the case of four layers. In probability that's called a Binomial Distribution and describes how to combine independent identical choices, like tossing four coins. If you flip them 16 times, on the average you'll get all heads **once**, three heads plus a tail **four** times, two heads and two tails **six** times, etc. **1-4-6-4-1!**

*(LOOPY2 is an ultralight tool for systems thinking ©2021 MITRE Corporation; cf Human Diffusion (2000-01-19), Combinatorial Interference (2003-09-10), Normal Distribution (2008-04-26), ...)* - * ^z* - 2021-09-01