Poisson arrivals spaced over a minute until a woman
Question
Customers arrive at a cinema as a Poisson process with rate one per minute. Independently, each arrival is a man with probability and a woman otherwise. Let count the arrivals up to and including the first woman. What is the probability that each of the first interarrival times is longer than one minute? Writing the answer as with coprime integers, give .
Short answer
6. Here is geometric with , independent of the gaps, each of which exceeds 1 with probability . Summing as a geometric series gives , so .
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Open the worked solutionLessons behind this question
- Defining the Poisson Process: Three Equivalent Constructions
- Conditional Probability, Total Probability, and Bayes' Rule
- Worked Examples — Probability Trees, Monty Hall, and Bayesian Updating
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