Question 361603: What is the probability that at least 2 people share the same birthday among 25, 50, 75, 100, 500, and 1000 people. I have tried to run a probability simulation in Excel to generate random numbers (this is required) but my results are supposedly incorrect. For 25 people, my probability was 0.04, for 50 people my probability was 0.06, for 75 people my probability was 0.1467, for 100 people my probability was 0.15, for 500 people my probability was 0.264, and for 1000 people my probability was 0.276. My instructor is saying "consider the number of possible birthdays and the number of people being used. In some situations the probability would be 1 or 100%". I don't understand this at all. The computer generates random numbers, so I don't control which numbers (1-365) are picked. Are my answers correct or am I missing something? Thanks so much!!!
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Try figuring the probability that none of
the people in the group have the same birthday.
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Then subtract that probability from 1 to get
the probability at least two have the same
birthday.
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If this makes no sense Google "statistics
birthday problem" and you will see how it
can be worked.
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Cheers,
Stan H.
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