471.Visible Heads in a Line
★★★expected valueCh. 6 — Random Variables and Expectation444+ Problems in Probability
Twenty people with IID heights from a continuous distribution stand in a single-file line. Looking from the front, a person's head is visible if they are taller than everyone ahead of them. Find the expected number of visible heads.
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When is person 's head visible? An indicator and a symmetry argument each position.
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