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Posted by u/Apwek 4 years ago
[Probability] Calculating Expected Value of a
raffle
Hey there, working on an expected value question and I know
generally how to calculate EV, but I just have a question about a
limited number of tickets sold type problem
Problem - Given the following information, what is the EV of a lottery
ticket after it is purchased?
Tickets Sold: One thousand $2 tickets.
One prize of $1000
Three of $100
Five of $20
Would the correct way to go about this problem be
$1000(1/1000) + $100(3/1000) + $20(5/1000) + $-2(991/1000) = -$0.58
I'm pretty sure it is, I just wanted to double check! Sorry for the
stupid question!
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ADdV 4 years ago
Almost. You assume only those 991 people lose 2 dollars,
but the ones that win something still had to pay for their
ticket. So actually they only win 998, 98 and 18 respectively.
Another way to do it is to take the sum of the amounts
(both won ans lost) and divide it by the amount of tickets:
1000 + 300 + 100 - 2000 = -600
-600 / 1000 = -0.60
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Apwek 4 years ago
That makes sense, thank you!
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