Ten white draws from coin-coloured balls
Question
A bag holds ten balls. Each ball was painted black or white according to a separate fair coin toss. You then draw a ball, note its colour and replace it, ten times in total, and every draw is white. What is the probability that all ten balls in the bag are white?
Short answer
About . The number of white balls is a priori and ten white draws have likelihood . Bayes gives .
Adapted from Wilmott, Frequently Asked Questions in Quantitative Finance, ch. 10 brainteaser 'Balls in a bag', p.351; question and answer rewritten by SelfMadeQuant.com.
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Open the worked solutionLessons behind this question
- Worked Examples — Probability Trees, Monty Hall, and Bayesian Updating
- Conditional Probability, Total Probability, and Bayes' Rule
- Sample Spaces, Events, and the Probability Axioms
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