When to stop drawing from 2 white and 3 black
Question
An urn holds white and black balls. Jesse draws balls one by one without replacement and may stop whenever he likes (including before the first draw). Each white ball drawn earns him and each black ball drawn costs him . Under the best stopping rule, what is his expected net result?
Short answer
A gain of dollars. Let be the value with white and black balls left: . Working up from small urns (, , , ) gives , so drawing is worthwhile.
Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.
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