Probability of a given number of a set of random numbers

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SUMMARY

The discussion centers on calculating the expected time to receive the number 6 from a set of random numbers {1,...,n}, where each number has a uniform probability of 1/n. The probability of receiving a specific number for the first time at the kth week is defined as (1-1/n)^{k-1}/n. The expected value of k, which represents the time until the number 6 is received, is established as n, although there is a discrepancy with other participants who suggest the expected value is n-1.

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  • Understanding of probability theory, specifically the concept of expected value.
  • Familiarity with random variables and their distributions.
  • Knowledge of geometric distributions and their properties.
  • Basic algebra for manipulating probability equations.
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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].
 
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Try computing the expectation value of k.
 
I did, I get n, where everyone else seems to get n-1.
 

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