You are right. I didn't know you were taking out the selected members. This calculation only is valid for a period where you don't put back any members in the selectable list though. Let's assume members can be chosen again after 50 days (1000 members). If you take the first 50 days your calculation is valid, and odds are 1 in 20. If you take an average period, where you can be selected on the first day, odds per day are just 1 in 950, so odds over a 50-day period are still 1-(949/950)^50, or slightly higher than 1 in 20.


Regards,

Auke


However, if you go on the assumption that a member can not be selected twice over a given period, then the odds become additive. I am not sure what all the criteria are for the original question of what the odds are for being selected as a UT Member of the Day.

>Mark,
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>My example was per drawing [per day]. Let's just say your odds are 1 in 1000 of being selected on any 1 day. Over a 20 day period, your odds become additive --
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>1/1000 + 1/1000 .... or 20/1000 or 1 in 50.
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>Adding probabilities is not right: in 2000 days you would get 2 in 1, which is obviously ridiculous. You could either calculate the probability of not being selected: (999/1000)^20 is the probablity of not being selected in 20-day period. So, the being selected at least once: 1-(999/1000)^20 (about 0,20).
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>Auke