What is the *“opposite” of sampling without replacement*? In a classical urn model *sampling without replacement* means that you don’t replace the ball that you have drawn. Therefore the probability of drawing that colour becomes smaller. How about the opposite, i.e. that the probability becomes *bigger*? Then you have a so-called *Pólya urn model*!

Many real-world processes have this self-reinforcing property, e.g. leading to the distribution of wealth or the number of followers on social media. If you want to learn how to simulate such a process with R and encounter some surprising results, read on!

Continue reading “The Pólya Urn Model: A simple Simulation of “The Rich get Richer””