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Probability of a given number of a set of random numbers

  • Thread starter Dragonfall
  • Start date
  • #1
1,030
4

Homework Statement


Each week you receive a random number {1,...,n}. You may receive the same number more than once. Each number has 1/n probability of being sent to you. What is the expected amount of time until you receive the number 6?


Homework Equations


I'm not sure what to use here.

The Attempt at a Solution


The probability of receiving any number for the first time at the kth week should be [tex](1-1/n)^{k-1}/n[/tex].
 

Answers and Replies

  • #2
104
0
Try computing the expectation value of k.
 
  • #3
1,030
4
I did, I get n, where everyone else seems to get n-1.
 

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