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The Insanity

Marc DuQuesne

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Going back to the probability I calculated (declared?), the numbers I used were:


-3,026 four year colleges

-180 day school year

-8 school shootings since 2014


(sourced above). Now there are some obvious assumptions I'm making- for example, that a given student actually attends all 180 days in any given year. There are others, e.g., that each school actually has 180 days.


It is becoming obvious to me how crude the calculation was, which obviously- was just to make a point. But now I'm sorta curious. I blame Jacen and Pav.


I think one big problem I made, and I alluded to this earlier, is just counting the number is not particularly relevant. It seems to me this is similar to when you flip a coin- the probability of a heads will always be 50%, irrespective of how many times the coin is flipped. Now let's say you flip it 3,026 times, or actually... let's just go with 10 times, and it happens to come up heads once. Well it would not be accurate to say your probability of getting a heads on any given flip is .098%. The mere fact that there was an odd, in fact, astronomically small occurrence that 9 tails came up in a row, does not change the fact that the next flip will be a 50-50.


So, in retrospect, I did not really calculate a probability at all. :(

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That being said (last post on this, I promise), it may still be helpful to work "backwards," so to speak. If someone had flipped a coin 3,026 times (or, even more than that... x 180 days x 2 years), and we got 8 heads... no one would believe that the individual flips were 50-50, or else, we'd be living in some cosmic phenomenon of low probability. Just knowing the end result may not help in calculating the probability with specific accuracy, but it would not surprise me that the resulting individual probability of an occurrence would end up in the general ballpark of what I originally calculated, even if incorrectly done.

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Jacen, thank you! I've been admonished before for playing loose with "odds" versus "probability". I'll do better in the future.


Carrie, I'm pleased to take responsibility for your curiosity alongside Jacen. :)


Just wanted to post a quick thought I had - perhaps we should look at school shootings as following a Poisson distribution? But are school shootings really independent events, or does the occurrence of one temporarily increase the chance of another one due to news coverage?

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164 Powerball jackpot winners from 2003 - Feb 2016.




141 killed in school shootings from Columbine (Apr 99) to Feb 2016.




Something wrong with your odds. Powerball isn't the only lottery.

I think there are a lot more people playing Powerball than people at risk of being attacked at a school. I'd estimate that there are easily 10 million tickets in play for Powerball for any given drawing


Over 70 million students in the US (not even looking at staff) are sold tickets for the school shooting 5 days a week. Still more lottery winners.


There were 3.3 billion Powerball tickets sold in 2016, and 1.9 billion in 2015 (data from here). Drawings are twice weekly, Wednesdays and Saturdays, so about 100 times a year (104 or 106 depending on year). So it looks like there are about 20-30 million tickets sold per drawing on average; I guessed a little low at 10 million but definitely the right order-of-magnitude. With the given odds of 1:292,201,338 for the jackpot and 3.3 billion tickets in play, I'd expect as many as 11 winning tickets in 2016 but there were only 7 jackpot winners last year. I'd expect 7 winning tickets in 2015 but there were 12 that year. But over 2015-2016, there were 19 winning tickets with 5.2 billion tickets sold, which is just about right. I could go back further but I don't see anything wrong with the Powerball odds. Frankly if there were something wrong with the Powerball odds, it would be a major news story. So, yes, while there are other lotteries, Powerball was the only one mentioned in this thread, so why should we look at all the other lotteries?


If something is wrong with the odds, it's with the school shooting numbers, and I think we all already expected that. If school shootings are not random, or at least not random in the same way that Powerball is, then the comparison is apples and oranges.


Also - Marc, "sold tickets for the school shooting 5 days a week"? What? Did a couple of your sentences get mashed together? Or are you approaching monkeygirl level of posting?

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