ImBillT
Well-known member
- Joined
- Oct 29, 2018
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I’m not gonna day I couldn’t use a refresher on statistics, but I THINK it should be at least as likely to draw twice in 20yrs as once in ten, and actually more likely.Good post, although I disagree with these two numbers. I calculated the probability for drawing at least once in 20 years. Here's my work:
P(draw zero times) = (.9)^20 = 12%
P(draw once) = ((.9)^19)(.1)(19) = 26%
P(draw at least twice) = 1- P(draw zero times) - P(draw once) = 1 – 12% - 26% = 62%
I didn't calculate the second probability.
Soo...why would the odds of something happening exactly zero times be different than the odds of something happening exactly one time? They should be th same. You’re still looking for a single specific outcome. What I did the first time was (.9^20) for the odds that it would happen zero times, which is 12.16%. Then subtract that from one for the odds that it would happen at least once at 87.84%. The odds that it would happen twice would be .8784^2, or 77.2% I now see that that would be invalid because that would be the odds that it would happen at least once in twenty years over two consecutive twenty years periods.
Doing it the other way would be 1-(.9^20+.9^20) which gives you 74.3%. This should be valid.
Edit: I think that’s still wrong. Perhaps your is correct. I still think that it should approach 100% of applicants drawing 10% of years.
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