Scheduling the Best Episode

8/10combinatoricsCountingprobability

Problem

A television series has n+1n+1 episodes, where n10n\geqslant 10. After watching the first episode, a viewer plans the rest as follows:

1. counting days from the day after finishing the first episode, the remaining nn episodes are distributed at random over 2n2n days; 2. on each day the viewer watches either nothing or exactly one complete episode; 3. at most one episode is watched per day.

The most exciting part of the series is episode nn. Let XX be the day (counted as above) on which episode nn is watched.

Part 1. Give the distribution of XX, and prove that the most likely day for watching episode nn is day 2n22n-2.

Part 2. Find E(X)E(X).

Answer

Solution

Difficulty8/10
Topicscombinatorics, Counting, probability

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