Cigarette packets used to contain cards representing such things as flowers, film stars or football teams. A complete set would comprise n different cards, say, and collectors would aim to obtain a complete set. Clearly, the first packet bought would contain a new card which would start the collection. The next card obtained might simply duplicate the first card, or it might also be a new card, and add to the collection, and so on. Obtain expressions for the mean and variance of the number of packets which must be purchased until a complete set of cards is obtained.

A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
Section: Chapter Questions
Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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Statistics and Probability
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Cigarette packets used to contain cards representing such things as flowers, film stars or football
teams. A complete set would comprise n different cards, say, and collectors would aim to
obtain a complete set. Clearly, the first packet bought would contain a new card which would
start the collection. The next card obtained might simply duplicate the first card, or it might
also be a new card, and add to the collection, and so on. Obtain expressions for the mean and
variance of the number of packets which must be purchased until a complete set of cards is
obtained.
Transcribed Image Text:12 Cigarette packets used to contain cards representing such things as flowers, film stars or football teams. A complete set would comprise n different cards, say, and collectors would aim to obtain a complete set. Clearly, the first packet bought would contain a new card which would start the collection. The next card obtained might simply duplicate the first card, or it might also be a new card, and add to the collection, and so on. Obtain expressions for the mean and variance of the number of packets which must be purchased until a complete set of cards is obtained.
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