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Suited_Jock
ITH Heart Throb
Joined: 20 Sep 2004
Posts: 3010
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 Posted: Fri Feb 09, 2007 4:59 am Post subject: Help me play private detective |
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Ok so slightly off topic but certainly to do with probability.
Our work has an optional social club where users can join and pay a nominal fee £2 ($4) which comes straight out of everyones wage packet. This money is used for two things... a social fund where monies are held for people to organize nights out etc The other is a monthly and yearly prize draw which everyone in the club is entered into...
The monthly prize draw is paid out in the following format
1st £200
2nd £100
3rd £50
with the yearly xmas draw paying out
1st £500
2nd £200
3rd £100
4th £50
There are 4 people from the company who are on the committe who meet every month lets call them w,x,y,z ..
Not that im bitter but I have never won one of these draws after participating in what say 14 since they have been running it however w just took home the xmas draw in 1st place for £500... this prompted me to look back over the results to find out y won the prize draw in april for £200.. x took 2nd place in october for £100.
I have data for 13 draws jan06 - jan07 inclusive...
There are approximately 350 members of this social club... should i be concerned???
Also in this data no person has won a cash prize more than once however noone is removed from a draw after they win. |
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cybrarian
Retired Moderator
Joined: 05 Dec 2003
Posts: 11244
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| Posted: Fri Feb 09, 2007 5:12 am Post subject: |
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| If w is Father Ted, I'd start to worry. |
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Suited_Jock
ITH Heart Throb
Joined: 20 Sep 2004
Posts: 3010
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| Posted: Fri Feb 09, 2007 5:21 am Post subject: |
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| cybrarian wrote: | | If w is Father Ted, I'd start to worry. |
Heh, took me a while to figure that one out then i realised id seen that episode.. with the car  |
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cybrarian
Retired Moderator
Joined: 05 Dec 2003
Posts: 11244
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| Posted: Fri Feb 09, 2007 5:30 am Post subject: |
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In 14 months, that's 46 draws (assuming there's a monthly the same time the yearly is done). With 350 people being drawn 46 times, by my quick calculation, which might not be right, there's about a 5% chance that no-one will have won twice.
That assumes that the same 350 people are in every draw.
Last edited by cybrarian on Fri Feb 09, 2007 5:56 am; edited 2 times in total |
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cybrarian
Retired Moderator
Joined: 05 Dec 2003
Posts: 11244
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| Posted: Fri Feb 09, 2007 5:32 am Post subject: |
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| I get that 5% by applying the same logic as in the birthday paradox - where you look at the probability that x people have unique birthdays. Substituting birthdays for draws, and days of the year for people is logically consistent, I think... |
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Suited_Jock
ITH Heart Throb
Joined: 20 Sep 2004
Posts: 3010
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| Posted: Fri Feb 09, 2007 6:08 am Post subject: |
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| i just added that bit in i was more concerned that the committee members seem to have an unsually high edge in this "random drawing" |
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cybrarian
Retired Moderator
Joined: 05 Dec 2003
Posts: 11244
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| Posted: Fri Feb 09, 2007 6:15 am Post subject: |
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If it's not random, both are relevant: the committe would probably underestimate the remoteness of not having any two-time winners.
The person you want to talk to here is z... |
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janeg
Regina Canada
Joined: 04 Oct 2004
Posts: 5112
Location: Somewhere down the crazy river
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| Posted: Fri Feb 09, 2007 10:47 am Post subject: |
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| cybrarian wrote: | If it's not random, both are relevant: the committe would probably underestimate the remoteness of not having any two-time winners.
The person you want to talk to here is z... |
He's getting rakeback. |
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