probability factor

Probability Factor.

This must be the only mathematical Surreal Posse post on the list and I think its possibly weirder than anything either the Quail, Jon or anyone else has come up with to date..

from

(Ryan Godfrey)

Subject: Totally, Totally, Totally Off Topic

So then John goes:

>At 12:16 PM 3/5/97 -0500, Gary Assassin <gsa@li.net> wrote:
>
>>OK, I'll admit, this IS entertaining. Can anyone tell me the odds on being
>>alive 11000 days, and missing all 7 NY shows because I will be out of the
>>country? I figured it to be 7/11000, but I was never good at probability
>>and statistics.
>
>If I'm not mistaken (I probably am) the odds on this would actually be far
>lower, calculated by taking the probability (as a fraction) that you'll be
>out of the country on any given day and then raising this to the power of
>(total number of Robyn-gig days), or 7. The number of days you were alive
>would be irrelevant except as a basis for determining the aforementioned
>figure. So, if you were out of the country, say, 1% of the total number of
>days within the given timeframe, you'd calculate it as 0.01^7 -- about
>0.00000000000001, or 1 in 100 trillion.

Geez, I haven't felt the urge to get this outright geeky in weeks, but I actually bothered to dust off the combinatorial probability to verifyJohn's numbers. It turns out that 100 trillion is a nifty approximation assuming the 1% figure (the actual number is closer to 1 in 121 trillion, but what's 21 trillion among fegs?).

Interestingly, the number of days Gary spent away from this sweet land o' liberty and the number of days he has been alive _do_ make a measurable difference to the numbers, even if their ratio (e.g., 1%) remains constant.

Gary, you didn't specify how many days you have spent outside this here country. If, in fact, the only days of your (temporary, and presumably voluntary) exile are the ones coinciding with those particular New Yorkshows, the odds of this freak occurrence drop to 1 in nearly 4,000,000,000,000,000,000,000,000, or 4 septillion (in the UK, I think the number's called something else). If, on the other hand, you've spent half of your 11,000 days in nations that don't rhyme with "esoterica," the likelihood jumps to a fathomable 1 in 128.24. Still, it's unlikely, to say the least.

Hey kids! Here's how you can play along at home! If d = the number of days you've been alive, and r = the number of dates Robyn is playing in your hometown this tour, and a = the total number of days you will have been (or were) in Europe/Mozambique/Upper Sandusky at the time of Robyn's gig in your neck of the woods, then the probability of your not being around for the show(s) is:

a!(d-r)!
_________ [I'm dividing here]
d!(a-r)!

The ! signifies factorial, which is the number multiplied by all positive integers lower than it. For instance, 5! equals 5 x 4 x 3 x 2 x 1.

But then, if you're morally opposed to punctuation marks posing as mathematical operators, John's rule of thumb will give you a pretty bitchin' estimate.

>Of course, real-world factors would also apply, such as how long the average
>overseas trip is (longer trips increase event dependency), what time of year
>you usually travel overseas, what time of year Robyn usually plays NYC,
>etc., all of which would decrease the odds, though to what extent it's
>difficult to say.

This is all true, but who wants to deal with real-world situations that only serve to muddy up the shiny galoshes of Abstract Math?

--Ryan Godfrey

Closet Math Dork

Here endeth this short excursion into math

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