The Classic Urn Color Change Problem

A Classic Probability Problem from your Early College Days. If you are still confused with Expectation Calculation, This Post can greatly help.

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Anyone who has taken probability class in their college or school is familiar with probability problems involving the classic urn (basically a bag) setup which contains balls of different colors and the professor asks you to find the probability of occurrence of some stupid pattern. This is one of those problems.

The problem goes like this…
You are given an urn with 100 balls (50 black and 50 white). You pick balls from urn one by one without replacements until all the balls are out. A black followed by a white or a white followed by a black is “a color change”. Calculate the expected number of color changes if the balls are being picked randomly from the urn.

Read my detailed solution at: The Classic Urn Color Change Problem

Rishi Dey Chowdhury
Rishi Dey Chowdhury
Master of Statistics

My research interests include Artificial Intelligence, Quant Trading, Deep Learning and their applications in Market Microstructure, Computer Vision and NLP.